Opinons on this? Bf problems

Ok so I've been dating my boyfriend for a year next month, I love him, he loves me, but recently Ive noticed something that drives me crazy, on Instagram he has an open account, and when you have an open account, crazy people follow you, so when these random girls he doesn't know, some not even showing their faces, just midriffs, follow him, he follows them back, I asked him about it and he asked how to put his account private. But even with these girls he sometimes likes their pictures, and their like of there stomaches. It annoys me. Now my boyfriend is kinda oblivious when he came to my volleyball practice once a girl stood right beside him and started flirting, he eventually pointed me out and said I was his girlfriend, and afterward when I told him about her flirting he said he didn't even know she was flirting, and he really didn't. Soo what do you think? Am I overreacting? I don't know. Because he always tells me that he likes that I don't dress slutty and stuff, but then he does that?