It's fine... but my son weaned himself at 18 months when I was 3 months pregnant because my breast milk turned salty :(
Yes it is. As long as there are no complications with regards to your pregnancy. As long as your pregnancy isn't complicated. I am currently 7mos pregnant and still breastfeeding my daughter who's almost 3y/o.
Totally OK I nursed my first born all the way through my first pregnancy and continued to tandem nurse him until he was two and a half and his little brother was 7 months. It was tough at times but I felt like it was totally worth it because it gave them a special bonding time too. It was also nice to still have special mommy one on one time with my older son, it helped him get over his jealousy pretty quickly.
I wasn't able to nurse while pregnant, my supply took too big of a hit and I had to stop. Be sure to mention it to your doctor and go with the advice.