It can be purely physical, but maybe its love…
1.You somehow always end up back together, whether it's after days apart, months apart, or years apart: Sex with other people is just not as satisfying and that makes your life just a little less satisfying as well. I was in a relationship for a year and not once did I truly enjoy having sex with the guy. He was nice, but there was no excitement. I would literally wait for it to be over. The minute I was single I reunited with my "friend" that I hadn't seen in 2 years. And it felt like we had never spent any time apart. AMAZING.
2.When you are together the simplest comment can become sexual and all of a sudden clothes are on the floor and you are not sure what happened with the last couple of hours: I loose myself in the moment when I am around my Sexual Kryptonite. By the time we are done with each other I have no clue what happened, but I always wake up smiling.
3.You develop a lot of firsts: Your list of sexual triumphs slowly gets longer and longer. All of a sudden you are bringing handcuffs and hot wax into the bedroom. You'd be surprised at some of the positions people come up with. When you can successfully do a handstand against the wall while he does the rest, then you have lived.
4.No one else measures up. There is always this person haunting your sex life: I mean full on haunting you. I have been right in the heat of the moment and heard another man's voice. "You'd have a hell of a lot more fun doing that with me." Talk about ruining the moment, especially when you know this is true. I could have been with a sexy man, who also came equipped with heavy artillery and my mind still would have wondered off.
5.You are mind-fucked: Logic and reasoning gets thrown onto the floor, right beside that little black thong. Feelings of lust easily turn to love and then back to lust again. He was on top of me, in the janitor's closet, on top of bubble wrap, and I had never been so turned on. Everything I felt was purely physical, I developed this aggression that I didn't know I had. It was true animalistic behavior. But the moment we were done I was ready to cuddle and talk about the future. Explain that.
So I don't know if it's purely physical or actually love, but I do know that this person will always have a hold on my life. There is no way to break a connection that strong. So first things first, figure out how you feel about this person. If it's physical then embrace what you have and enjoy the ride. But if its love take the leap and tell them how you feel, they are not going to wait for you forever.