Congrats!!!
Don't worry... You are fine to continue normal activity lifting, working out, etc. unless you have complications and your doctor tells you otherwise or it becomes painful. I am a few weeks away from #3 in 4 years and lift my 2 year old (30lbs) all the time and sometimes my 3 year old (32lbs), and sometimes both at the same time - no problem. The less you carry LO#1 the more independent they become which is good because then they won't be as upset (maybe) when you have a newborn and are unable to pick them up. To this day, not much has changed with the way I interact with my other kids. Some days I'm more tired so we aren't as active, but still doing lots of arts and crafts, reading books, etc. HTH