Found out boyfriend cheated, now depressed?

Well, about last month I found out that my boyfriend cheated on me 2.5 years ago when we had just started dating. It crushed my world. I thought he was the one person I could always trust. It hurt that he lied to me for nearly 3 years about it and he didn't end up telling me, I found out another way and then he confessed. Well he's trying everything to fix it so I decided to stay with him. But now, I have grown into a depression. I had recently lost 20 lbs and I'm starting to gain it all back, I no longer eat right or exercise, I signed up for a Law School Admissions Test course to help me study for one of the hardest tests of my life. It cost me 3,000 dollars and in the past month since I found out, I haven't done more than 3 hours of homework. I am supposed to be studying a minimum of 8 hours a day for this test. But this issue has got me down so bad that I have no motivation or concentration. I decided to forgive him but I am now jealous and insecure and have constant nightmares about this situation over and over every time I sleep. I spend all day in my bed sleeping, or laying in bed. I don't know what to do, my boyfriend is suggesting that we go to a counselor and I really think that's a good idea. I just don't know how I can force myself out of bed and become motivated to eat right again, exercise, enjoy life and study? I tried forgiving him, but it's a long battle and I've grown tired and the depression isn't helping. I think most of the issues are subconscious and that is why they appear in my dreams. Then my dreams end up affecting me throughout the day. I just need advise on what to do to conquer this depression!!!