I'm 12 weeks now and I had a big scare working out! I was lifting and lifted more than I should have and started having pains in my stomach.
My doc told me to just listen to my body. If it feels wrong, it IS wrong! He also told me not lift heavy and cut back even more after the first trimester, and to just do a less intense-modified version of my previous cardio routine. I love to spin and run, and I've still be doing both with no issues. I have started going not as "hard" in spin class and jogging instead of running and its been working out great for me.
I was told exercise is very good during pregnancy. Gives you energy, helps you get your body back after the baby, and helps makes delivery easier!