Not really sure what exactly you're describing. Your profile says you're female and doesn't say how old you are. But your post sounds like a young male, but we don't know how young. Either way, you have a crush on someone who apparently doesn't have a crush on you, if I get your drift, and you're thinking a lot about it. But that happens to everyone. Romance is hard. I also have never heard of too much thinking leading to shortness of breath or chest tightness. Anxiety can do that, depression can do that, but not just deep thinking. As for illusions and delusions, that refers to psychosis, and you definitely don't sound like someone who is psychotic and having delusions. So I'm not clear on just what your doctor was implying unless it was based on something he noticed about you. Anyone with a creative or intellectual mind is going to do a lot of thinking, and sometimes at times they'd rather be at rest, but that's life. Bottom line here, thinking isn't a problem, it's what people do who haven't shut off their minds. Anxious or depressed thinking, on the other hand, is obsessive and bothersome and troubling, and so yes, that kind of thinking is very unpleasant and can cause the body to follow by feeling unpleasant. But romance, again, is always going to present problems, especially unrequited romance, and there's really no cure for that except time, success, or admitting failure and moving on. Peace.
So, glad you went and got checked out for chest tightness. That's important to rule anything out. There is a Relationships forum that you might find helpful here at MedHelp that you can talk about your girlfriend. I do think relationships that aren't easy can cause a lot of internal turmoil and our body reacts even when we aren't 100 percent aware of it all.
I'm trying to follow what you are talking about though . . . you are trying really hard to get her to reciprocate feelings you have for her but sense she doesn't have for you?