Hi Alex,
I have two boys, 2yr & 9mo. I was pregnant with my second when my first was only 6 months old. I would suggest to ask your doctor of course, about any concerns you may have. I didn't exercise during my pregnancy, or before, but have always read that if you are active before pregnancy to continue during. There are only a few things you're not able to do, aerobics, etc. I had to pick up my 6 month old all the time and I was nursing him also. I nursed him until he was 13mos., I was 7mo. pregnant. I consulted my doctor about any questions I had, and everything turned out well. Just remember to take it easy, and don't over do it!