Am I overreacting?!?! Or have I just become the potential relationship-wrecker????

Okay....I really, really, really need some advice with how to handle this because I'm not sure what to think.

So this past weekend, my stepmom held a big party in celebration of her birthday and invited relatives from both sides of the family. Among them, was my cousin, Zelne (alias) and her super hot boyfriend, Heinrich (also an alias). I'm the same age as Zelne, though Hein is a year older and he's at my school so we see each other quite often. I've never actually gotten along well with Zelne, however recently we've resolved our differences and we're pretty close now (she doesn't know I'm gay, though.)

In any case, on to my dilemma.

The party's in full swing and everybody's having a good time. I'm sitting next to Hein who in turn is sitting right next Zell. Now up to this point, for reasons unknown, Hein has become really touchy-feely with me. At first it's just a friendly hug and a gentle pat on the back, then an amicable squeeze on the shoulder. However, as the evening progresses, he starts doing it more frequently and slowly it starts fraying my nerves.

Now, at the dinner table in full view of everyone, including Zell, he starts stroking my leg. Even though I am freaaaakkkiiiiing out at that moment, I try my best not to show it. I steal a few nervous glances at Zell, who sees it but is too engrossed in conversation to make a comment.
I look at Hein. He looks back at me with a dreamy expression on his sexy, tan face which, even though I try to resist as hard as I might, causes something to stir down under......

That's not the worst....soon they deal out shooters. I can't stand the taste of alcohol, even though my family presses me to try it. When Hein is handed his glass, he tips back half and slams it in front of me.

"Are you serious???" I ask.

"Yeah," he says, "It's only half. Go on. Do it for me."

<Major freakout episode in which I stammer and eventually laugh it off nervously>

"I don't know. I hate alcohol"

"I drank half. I already made it good for you"

<Freakout. Zell hears every word but she just smiles and strokes his hand>

"Go on, Josh!" She says, "Do it!"

I hesitate....then eventually tip the glass back. The family cheers heartily and applauds me...even though my eyes are watering from the potent, vile liquid.

Hein looks at me with the same sensual expression as before and says, "I'll make you feel so good tonight."

<EPIC freakout. Zell reacts to this and kicks his shin. However they both laugh it off as a joke>

And so the night goes on.....

-----------------------------------

These events are still milling in my head.

I'm unsure how to react to this.......? What if the guy actually has a thing for me??!!! I don't want to be the homo with which the seemingly heterosexual guy cheats his girlfriend on....especially since his girlfriend is my cousin! It's going to be extremely hard for me to function properly in his presence since I see him everyday at school.

Then again....I might've misinterpreted a lot of the signals he sent me, and overreacted as a result. I just don't know.

Any advice on how to carry through with this???? I'm desperate!