Yes, there is a good chance that you are partly feeling this way because of the quarantine.
It’s perhaps a combination of the isolation that you are currently experiencing in general and how the semester has been prematurely interrupted.
It was easier for you not to miss him like this over the winter vacation because you were already mentally prepared for the semester to end.
This made it easier for you to cope with not seeing him for months.
With the premature break from the semester that has been caused by the quarantine, you didn’t really have the time to prepare yourself mentally to not see him again for a period of time.
On top of this, there is uncertainty on when the college will reopen, if it does at all for the remainder of the semester.
This uncertainty adds even more anxiety as you don’t even know when you will see him again.
So yes, the quarantine has most likely had a big hand in making you feel this way.
As far as his relationship history, perhaps his three year relationship didn’t end well.
He may even still have emotional issues caused by that relationship that he hasn’t resolved.
Whatever the case, he simply doesn’t seem to be fully open emotionally.
That would have to explain some of his erratic behavior when it comes to you. One moment he mentions that he just wants to be your friend and the next moment he can’t stop staring at you.
His erratic behavior would indicate conflicting emotions that are being allowed to dictate how he behaves.
You are more so bothered by guys that you are interested in who don’t approach you than by guys in general who don’t approach you.
That makes things clearer.
Developing strong feelings quickly for someone that you like also makes this whole situation with guys that you like who don’t approach you that much harder to overcome.
Try to develop the mindset of making the guy earn those feelings.
You are giving these guys that you like too much benefit of the doubt. You create a story about them and what they must be like in your mind before they have earned it through the process of interacting with you.
If you make it a habit to tell yourself that you don’t really know this guy, regardless of how popular or cool he may seem, it will make it easier for you to stop developing feelings so quickly.
When you develop feelings so quickly, you make it that much harder for a guy that you like to approach you because your body language is now tensed up.
You have built that guy up to such a level in your mind that you can’t imagine matching him and as a result, your body language around him becomes taut and closed off.
Again, if you can avoid building these guys up in your mind and always tell yourself that they have to earn those feelings in getting to know you first and vice versa, you may have a much more relaxed body language around guys that you like.
This may ultimately make them feel comfortable enough to approach you.