I think I no longer like my boyfriend

We have been together for 3 years now. He is 14 years older than me. Lately, I stopped finding him interesting and u actually started seeing the opposite. I find him lazy, boring and I don't feel like he is investing in our relationship. He doesn't give me any attention and did not even get me anything for valentine (I wasn't expecting much, a letter or a single flower would mean the world to me). As I'm a grad student, I have many friends, some of them are boys. And I find it weird when those friends do give me much more attention than my boyfriend. One of them in particular confessed that he likes me and he is really working hard to get my attention. He knows I have a boyfriend but still... Im just feeling lately that my boyfriend is taking me for granted.