HELP!

I have been going through stress about school and work. I was supposed to stop working and start student teaching, but then it fell apart and i have to wait till september. I was begining to worry and freak out. Now, I freaked out on my girlfriend of 7 years thinking she was cheating, (she wasnt), and was all needing her to prove that she wasnt. She proved that she wasnt, then i freakekd out thinking she didnt love me andy longer, but she does... now I feel like I need to run away because I am going to hurt her... now i have these terrible thoughts of her with someone else, and it makes me so upset. I am with her right now, and i go from feeling fine like there is nothing wrong, to being scarred and and crying and throwing up. i dont want to loose the best thing that has ever happened to me. I love her with all my heart and i dont want to screw up. Anyone have any suggestions. she is totally being supportive, but the negative thoughts in my head along with my paranoid ideas are killing me insie