Omg

Shame on your GP who prescribed Cialis. The GP should have talked to you to find out why such a young man asked for Cialis. Had the GP done that, you would now be under the care of a psychiatrist.

You describe a lot of depression, anxiety, restlessness, low self esteem, a lot of "existential angst", being directionless, but no paranoid delusions. It seems that you were drawn to eco conscious movement because you are trying to find stability by holding on to an external structure whose foundation appeals to you intellectually. Again, this does not look like a delusion, and that you worried it could be a delusion makes it especially doubtful that it is a delusion, but let us see what a psychiatrist has to say. Go to your student health services and request psychiatric intake. That would be step #1. Then you can inquire about psychotherapy, as it would be nice for you to talk to someone regularly, especially as you are making big career decisions for yourself.

Don't use Cialis again - treat anxiety, which is the root cause of your issues (plus depression), and Cialis doez not treat depression and anxiety. That you do not have ED with the woman you know well is consistent with the hypothesis that your ED is from anxiety (which is good news because anxiety is treatable; some of the diseases that really require Cialis are not treatable). If having sex with ex is mutually pleasurable, by all means go for it, but don't conclude that she is the one simply on the basis of this artifact. In general, try to limit how many decisions with long term impact you are making at this time (that would include postponing any thinking about who is the one).

You reported a fair number of hookups, so when you go to student health services, get your self tested for STIs and make sure that you are up to date on all the vaccinations that prevent STIs.