I get suspicious if a girl shows clear interest in me.

Well, for starters: a girl that gives that much attention WANTS that much attention.
And those girls, will drain your soul! ;)
On a more serious note, they DO want your attention, they might just like you, man. Own IT!
There is nothing wrong with not ever having a girlfriend before, or still being a virgin. Not having a girlfriend means that you don't have to put up with drama. Jealousy. Complaints. The giving of CONSTANT Attention. So, more power to you! And sex, it's overrated, to say the least. Do it when YOU want, don't be a follower. Maybe a girl IS up to something, maybe she wants to make some other guy jealous by being all up on you like that. Maybe she's doing it to show her friends that guys DO let her do that. That she is indeed desired/wanted.
You can go ahead ans give her attention, but think nothing of it. Honestly, I know girls like that [I am no longer associated with them! YAYYY!] And they are just attention wh*res.
You could be suspicious because you are not used to it. In the future, I will almost assure you, that the girl you will be most attracted too, WILL NOT be one of these girls. So you can either, go with the flow and give them attention and just blow them off when they are NOT doing that to you, OR you can half-a*s the hugs you give back and not give her the attention she very much craves from you. Don't worry about being suspicious of their actions, it's a phase that will continue until they are older and get F**ked over by guys. It happens. GOOD LUCK!

maybe you are just on your guard, thinking she wants something, trying to use you, etc... but that's what people are. same when they like you they are nice or flirting because they want you or want to be with u, so if you want their company in return then why not enjoy them a little. can mutually benefit