Please help me...im so upset?

I have been dating a woman for 7 months and all she does is point out my short comings and make me feel like I am not good enough. She is a 8 years older than me and it almost feels as tthough she is always taslking down to me. She wants me to be perfect and I guess she wants me to be somebody I am not? Is this an emotianlly abusive realtionship? She also leaves me when she gets pist off then always comes back a few days later after punishing me ruthlessly. What the hell should I do? She buys me all inds of gifts and stuff and then says im not thoughtful enough. No matter what I do, all i ever hear about is what I don't do. I never get any positive reinforcement at all. I also always have to cover my bases as she checks my email and everything else. PLEASE HLP