I'm almost three months pregnant!

I found out I'm nearly three months pregnant today, I had no idea! I did miss my period, but I'm on Depo so I didn't know. I also had extremely tender and swollen, but me being stupid, I didn't think anything of it. Anyway is been three months, and I've been drinking large amounts of coffee everyday, drinking alcohol on the weekends occasionally, I'm worried for my baby! What can I do othe that go to the doc to maybe he'll? How much damage could of been done in these three months?