Freshman 15

I just finished my first semester at college and as hard as I tried to work out and eat healthy those late study nights and little sleep got the best of me! :( I think I gained 15 lbs or a little less but I feel huge and the biggest I've been in a long time! I'm used to always being active and I love working out but being away from my normal routine for the first time at college was a new experience. I'll be heading back next month for the spring semester and I want to make sure those 15 lbs disappear and id like to lose a few more than that and be in a good healthy shape! Before college I weighed about 140 lbs and I now weigh about 155, I would like to weigh about 125!

I've never really had a steady diet or a strategic workout plan, but I'm looking for both! There's just so much out there that I don't even know where to start or what to try!! Any suggestions or advice would be so appreciated!