Ive been dating this girl for about 6 months, and things have started changing.?

As i said its been 6 months in the best relationship of my life. Lately though she has started being meaner to me, calling me fat (I've struggled with weight issues in the past) and stupid (I was diagnosed with ADD and general anxiety disorder this year) it doesn't bother me a lot where I get pissed. Its just like if she knows this stuff why is she trying to offend me. The flipside is she can also get very clingy and affectionate. She loves kissing me on the cheek, and cuddling on the couch. She tells me she loves me constantly over the phone and how I'm her world. I'm wondering what she could be going through? Also, if this relationship is worth continuing. Her name calling doesn't bother me im just wondering if you think there's anything wrong? There was also a group of girls that got pissed I asked her out and some still talk to me and you can tell still want me...should I pursue them at the cost of making a huge mistake and breaking my girlfriends heart?. I've helped my girlfriend through her alchoholism, she helped me through dark times when a friend committed suicide. i know this is long and complicated but i need help.