Hi Michelle,
Congratulations on your pregnancy. :-) I don't think it's necessarily your age, although that certainly can make a difference. I had my first at 30, second at 31 and third at 38. I was very sick the first two times, very nauseated. In the first pregnancy, I had all sorts of aches and pains that nobody could explain. In the second, I had preterm labor from 26 weeks, so that accounted for those pains. In my third pregnancy, I was very nauseated, but this time I had a 6 yr old to take care of, so whether that was the reason or not, I was able to get up and around and do things that I absolutely could not have done the first two times. (My first pregnancy did not have a happy ending, so no child for me to take care of while pregnant with number two.)
Because I wasn't as nauseated, or didn't seem to be, the third time, I decided it must be a boy (girls the first two times). It wasn't, a girl came out. :-) I was much more tired, though, at 38, than I was at 30 and 31. I was on sick leave the entire pregnancy, which was good because I wouldn't have been able to work, as tired as I was. And now, at 39 with a soon-to-be 7 month old, I definitely feel my age, but it is so worth it.
Good luck! If the cramping doesn't subside, I think I'd go to the doctor. The tiredness sounds pretty normal.