Sound very shit. I think it would be beneficial to see a doctor in a general sense about this for some long term issues.
I know we've spoken about this travelling thing before as I suffered from this pretty badly between about 19-22ish. I was so terrified to leave the house especially to get on a train or a tube because I was worried I'd need to do number 2 and would be stuck underground or not be able to get to a toilet in time. I used to take HOURS to leave the house as I'd be constantly trying got empty my bowels or I'd end up taking a lot of Imodium and be doubled over in pain for 2 days afterwards. In the end, I stopped leaving the house althogether.
I don't know what made me decide to change (I think my bf at the time was getting fed up) but I started my own kind of exposure therapy. I'd just go into London (at the time I lived in Essex) and wander around and go home. At first it was fucking awful, sometimes I wouldn't go, or I'd get to the station and come back, and sometimes I had panic attacks but what never ever happen was the main thing is worry about. It got easier each successful trip and it's like my brain then learned "it's alright nothing bad will happen". Basically what I'm trying to say is a) you're not alone in this. I reckon loads of people have this same issue and b) you can overcome this. Maybe CBT might be good for you or just facing up to shit and trying it out but from experience, medication won't necessarily help that. It's almost like it's been programmed into us and we need to erase it rather than numb it, if that makes sense?
As for the other stuff, I'm not sure I can help too much but how is your self care routine? What are you doing to help yourself? I have found I go through these phases and that I need to exercise permanent constant self care or I'm screwed. I know if I don't do X, Y will happen and I don't want Y to happen.
Take care of yourself please. Be selfish. Take space when you need it. Always remember to breathe x