First of all, what do you define as "things that only gay guys will do"? A man might think that cuddling with another man is considered something only gay guys do, but in this society where the idea of a fragile masculinity has started to become more recognized, it could be that he just doesn't have the idea of a fragile masculinity and doesn't mind doing those things only gay guys do. (Also read Is It Normal to Have a Man Crush?)
As the title suggests, it can be hard to tell whether or not he's actually straight. He may say he is because he hasn't come out yet, especially to his closest friends and family members, but it could be that he's actually straight.
So, how can we know that he has feelings for you? First let's start simple with signs of a normal crush:
If you both go to the same school/university or work in the same workplace and you catch him occasionally trying to catch glimpses, then this might be a sign that he has at least a teeny bit crush on you. (Also read Why Does My Crush Look The Other Way When He Sees Me Could He Be Shy?)
He might not even talk about something important, just texting you asking what's up or how you're doing. (Also read How to Tell If Your Gay Friend Has A Crush On You.)
Just the two of you, no other friends around. He might shake it off as an excuse to kill some free time, but it might be a sign if he only invites you and no other friends. (Also read Best Ways How to Talk to Your Crush If You are a Gay and He’s Straight.)
Now, it's important for you to know that a straight man could never return your love. If you have engaged in sexual activities together before, then that's it. It's nothing more than sexual pleasure mainly for himself. He will go on to fall in love with women because that's what it is, straight.
Unrequited love is painful, and no one should have to go through that, so now how can you get over your straight crush?
Even if the signs are there and it may seem like he also has feelings for you, if he constantly pushes the straight agenda then it's time to remind yourself that it's one-sided. (Also read Can a Straight Guy Fall in Love with a Gay Man?)
There's nothing you can do to make him suddenly fall for you, and you can't force him to like you either. Even if he's closeted, you can't force him to come out when he's not ready.
Go out there and meet someone new! Who knows, you might even meet another guy who'll actually fall for you.
Instead of sulking in your bedroom all day thinking about all the possibilities of your straight guy friend falling for you, keep yourself occupied. Find new hobbies, do something that makes you feel happy.
Just remember that thinking about someone you know will never like you back is not worth your time and energy. You are much better off doing things that are productive and brings a lot of positivity into your life.