Warning: There's some TMI (#1 and #2 talk) in here.
About a month ago I went out of town with my sister, cousin and cousins two kids to the states (we're Canadian) and on the way back near customs I really had to pee (we couldn't go anywhere for a washroom). This plus being a bit overheated just spiralled me into a major panic attack. Finally cross the border and I'm feeling sick, find a bathroom and go #1 and #2 plus feeling incredibly nauseated. Drive a little farther towards home, had to stop soon after at a gas station for more #2 and only managed to leave after draping cold wet paper towels over my neck and forehead. Manage to get to my sisters place where my dad meets up to take me home (~15 minute drive), had to close my eyes and feeling like I had to puke.

Next few days still feel off, I hurt something in my back (my mother believes I pinched a nerve in my back, probably when writing when I had to pee and was anxious) so I didn't feel normal. This plus some remaining nausea made me not have a happy next few days.

Proceed about a week later. Made plans to go to the island (for context, that's a half hour drive, ferry for 1.5 hours, another half hour drive) with my dad and uncle. Make it to the ferry, started feeling nauseated right by the docks. Realized we had forgotten apartment keys (overnight trip staying at my current apartment) so had to drive back. That's when things got worse. Felt like I had to pee again and near the end feeling like I have to #2. Make it home, use the bathroom feeling nauseated and doing #1 and 2. Try to drive back to ferry, make it halfway before I keep feeling nauseated and started to cry that I wanted to go home (I was frustrated and upset and Dad wasn't listening (my Mom is the one who understands anxiety)).

Went home. Did minor driving since then but a few times I had to go home early because nausea/sick feeling returns. Starts getting better. Some days didn't feeling great but managing (back pain made me anxious).

Then yesterday. I'm anxious already because my Mom just left to take care of my grandma so my grandpa could come out. Plans occur of possible spending a few hours in the states with grandpa as well as go to the island for apartment-hunting. Already nervous about driving in the car.

My dad and I went off to Costco. I had to pee in the car after we left. No biggy, Costco has a bathroom. Try to hold it at first but start feeling anxious again and went to use the Costco washroom to pee. Still am not feeling good as I return and we continue to shop. Stop to grab supper (cheap hotdog and soda). I take a few bites then wrap mine up while dad finishes and we have to leave because I'm feeling sick like #2 time.

Mini panic attack trying to leave (guy was trying to park next to us and damnit I needed a washroom at home), fine for most of the drive with deep breaths. Make it home, #2 and feeling awful. Probably in the washroom for an hour, on and off (on iPad trying to distract myself half the time).

Maybe an hour later, take a couple gravol, back in washroom. After this time things get better. Maybe two/two and a half hours after we returned I'm feeling okay again, eat my hotdog, have some soda and water etc (had been drinking water since I got home). Was fine until I wrote this post for another site (nobody responded to me so I found another forum). Had a major anxiety attack last night, mom didn't answer her phone (on silent) and had to use the bathroom repeatedly. Eventually popped a couple of pesto bismol and fell asleep like three hours after the start of the attack.

Today, I'm not feeling great. A stomach upset, legs hurt (from tensing I believe), mostly nausea. Grandpa is in town and wants to go out for dinner. Honestly I just want to stick around home until my Mom gets back. (I'm twenty but my mom is my rock and has had anxiety a long time so knows how to deal).

I should note anxiety isn't caused every time I have to pee really badly (tested via the I-don't-wanna-leave-my-warm-bed method).

My problem: How do I get past this? The major triggers seems to be when I have to use the washroom when in the car but any time I'm in the car I'm not feeling good. Pretty sure it's psychological now, anxiety based after the bad anxiety attack (haven't had one that bad since I got on medication). I need to go places and be okay in a car. I've tried listening to music/cold air of AC/conversations but it only helped sometimes. Advice, fellow anxiety people?
TL;DR Major car sickness each time in car after major incident a month ago. How do I get over it?

Footnote info: I'm 20F, been on 200mg of Setraline (I get generic Zoloft) since I was about twelve-thirteen (it started low and gradually increased to the same as my Mom who also has anxiety), haven't seen a therapist/psychiatrist/etc since diagnosis (went for 6m-a year according to my mother (I have very little memory of going to therapy other than once, to be honest) and was under the care of the doctor who had known me since I was little. Since she retired a few years ago we just get refills for prescription at clinics nearby.

I'll do an intro later today. Meanwhile....help?