Well done for breastfeeding into toddlerhood. And congratulations on your pregnancy. It is unlikely that breastfeeding is affecting the way you feel in this pregnancy though I do sympathise with the extreme tiredness and sickness. That most likely pregnancy related. Breastfeeding through pregnancy is unlikely to harm the fetus or the pregnancy. If a woman has had previous difficulties in keeping a pregnancy to term then it may be suggested to stop as a matter of caution not from any evidence that it would make a miscarriage more likely. The fetus always takes what it needs first from a mother's body so there is no danger that it will miss out on something vital. You may find that after 12 weeks the symptoms you are experiencing would subside completely anyway. If you are keen to wean from the breast anyway that is also fine. How you do it is down to you and your toddler. I would suspect that at 18 mos it could be easier or harder to do it than at 11 mos as the previous poster has experienced. Your toddler may be quite vocal at expressing his loss and that can become a real emotional challenge for you. Maybe contacting LLL can point you to a support group in your area (including virtual FB ones) where mums feeding toddlers support each other including support each other to gently wean from the breast. Your milk supply is diminishing now anyway and will soon become colostrum. I found that feeding through pg for the last night feed was an easy way to send my toddler into dreamland rather than having to battle for half an hr/ an hr/ whatever with bedtime issues. Especially considering that I suffered SPD from 12 wks pg and didn't have the physical mobility to cope with it.