Friend acting weird around my girlfriend

Ever since going out with my girlfriend, my friend has been acting abit weird around us. We are all living together so privacy is already something out of the question..but even when we do get some alone time he would be there...asking what we're doing/talking about...I think he may be away from female/ girl interaction for quite a long time. The most recent thing though is that he went overseas to Canada and when he got back he bought my girlfriend necklaces and earings...I dont know if I'm thinking too much about it but I think it would be weird if the situation arose where he would say something like "oh, you're wearing my necklace" ...