Pregnant and breastfeeding

I just found out I’m pregnant with #4 and my 19 month old who has been weaned for a few weeks suddenly started wanting to nurse again. I’ve never nursed while pregnant as I wasn’t able to and I was told that nipple stimulation is bad. Is it ok to let my 19mo comfort nurse? Is it going to hurt the pregnancy? I know people have done this and tandom nursed before but up until now I’ve never been able to even get pregnant while breastfeeding so this is completely new to me. It’s not going to risk miscarriage right? TIA