As long as you don't have a history of pre-term birth or other complications, it is totally fine to nurse through your pregnancy! Your milk supply will probably dwindle significantly with the hormonal changes in pregnancy, but there may still be a bit of milk, especially later on. Here is my story of tandem nursing and pregnancy weaning:
My oldest, DS, weaned at 17 months, when I was about 7 months pregnant with DD1-- he was always a "down to business" breastfeeder, used a pacifier for comfort sucking, and had bottles of EBM while I was at work (I continued pumping until shortly before he weaned). DS did ask to nurse a couple of times after DD1 was born, but his latch, never great, was really bad, so I would express milk into a cup if he asked for it-- really only a few times.
DD1 loved nursing from the moment after she was born, was still actively nursing when I conceived DD2, and told me in no uncertain terms that when the baby (DD2) was born, she (DD1) would have all the milky she wanted, and the baby could have a bottle. DD1 was a very high needs baby, meeting all her suck needs at breast-- I don't think I put her down for more than 10 minutes until she was about 8 months old, and she nursed about every hour- hour and a half until she was well over 2. Nursing was very uncomfortable for me as the pregnancy progressed, especially as my milk supply dwindled, but DD1 still nursed a few times a day for a few minutes. When DD2 was born, DD1 was 27 months old, and eager to nurse as often as the newborn DD2. DD1 nursed less and less frequently, and fully weaned about a month before her 4th birthday.
DD2 was a quiet, content baby who always nursed well (I always said I could have 4 more like her!), but found her thumb early. She nursed frequently, latched well, but sucked her thumb to soothe. She's still nursing a few times a day (morning, nap, bedtime, and if she gets a boo boo) at 28 months, and still sucking her thumb. I'm 3 months pregnant, now, with #4, and starting to find nursing pretty uncomfortable. We still nurse for a few moments a day, and I plan to tandem DD2 and the new baby!
Sorry for the novella! Good luck, OP!