I don't drink alcohol. My boyfriend likes a drink every now and then, and sometimes he'll go out with his brothers and friends and drink a bit more. I don't have a problem with it. He's old enough and wise enough to make his own decisions, and besides, I trust him.
He knows that I don't like being around drunk people, though, so he might have the occasional pint at home, but he won't get drunk - he reserves that for his nights out. Now, I wrote all that not to make this about me, but to show that mutual understanding goes a long way. Of course, to understand why your boyfriend is being like that, he needs to share his thoughts with you.
It's perfectly fine for you to have a drink. If he's acting the way he is because of a lack of trust, that's a bad sign. If he wants to control you, that's a very bad sign. If he's concerned about your well-being, he needs to understand that you've thought things through and are being sensible. Which then comes down to trust once more.
This is very much his problem, and whilst you can reassure him, there is a limit to how much you can be expected to do so. For him to treat you the way he has and to still be annoyed several days later is rather worrying. Especially when you haven't done anything wrong!