I am 32 years old, and when I was in junior high school I was the kind of guy who was always very spontaneous and relaxed, and this made it very easy for me to get new friends and to become popular among the girls and things like that.
However, some times in 2002 I gradually started to become more and more "serious" and socially awkward (I think that my parents' divorce that year was one reason, but also the fact that I entered high school and lost lots of my old friends from junior high school) and this caught me in a vicious circle where I started spending more and more time for myself - I did sometimes hang out with old friends and have a lot of fun with them, but this became more and more uncommon until I became depressed for a couple years.
I managed to get rid of that depression some time around 2009 I think, and I started to feel a lot better for a few years and had a relationship with a girl for a while, and for a while I felt genuinely content.
But in 2015 I entered college, and in the beginning I noticed that several of my classmates liked me and tried to talk to me and invite me to parties and things like that, but I was still a bit too careful and always skipped everything, until they stopped trying and seemed to become intimidated by me instead (and I never meet them any more since I took a one-year break, so I am one class behind right now and don't really belong to any particular class, since I have a few important unfinished courses that I am trying to catch up on).
This has made me become a real loner there, and I never spend time with anyone at all at my university (and my university is more than 500 miles away from home).
This is starting to really make me feel extremely frustrated, partly because I feel that I could easily become my "old self" in the right situations (that is, in situations where I have a concrete reason to talk to other people) and also partly because it makes me feel an almost overwhelming longing for the times when I did feel confident and had several friends and was considered an overall cool person.
And I don't know quite how to get out of this either, because the times when I do try to act confident it will always feel fake, and I quickly lose that initial small confidence if they don't play along quickly enough, and then I am back at square one again.

It's much easier for me to be my old confident self when I meet my classmates from junior high school, because they actually expect me to act that way, so I don't feel held back in the same way among them.

Do you know any good way to get rid of my anxious behaviour at my university, so that I can start acting like my old spontaneous self there as well?
I have considered joining some social club, like fencing or something (I know that they have a club like that there, and I have always considered trying out something like that anyway) just so that I can start to meet people there and learn to become confident among them, and in a setting where we actually do something fun and entertaining together instead of just sitting and doing serious school work.