Gemma, both of those are very common in pregnancy, and neither means you are doing anything wrong.
Milk supply often drops a long way during pregnancy because of the hormonal changes, whatever you do, and for many people that drop comes partway through. It is not a sign the toddler has taken anything, and at 22 months he is getting his nutrition from food. Feeding with very little milk is not pointless if you both want it. For many toddlers it is about comfort, closeness and routine as much as milk, and that has value. Some toddlers wean themselves at this stage because they dislike the change in taste or flow; others carry on happily, and some go on to feed alongside the new baby.
The skin crawling feeling is nursing aversion, and it is widely reported in pregnancy. It is often put down to the hormonal changes of pregnancy, and it is not a judgement on your bond. It is completely fine to set limits because of it: fewer feeds, shorter feeds, counting down, feeding only in one place. Limits are not cruelty and they are not the same as weaning unless you want them to be. If you decide you want to stop, a gradual approach is usually gentlest for both of you.
Our new piece on breastfeeding a toddler covers limits and the comments you'll keep getting, and breastfeeding while pregnant covers supply, aversion and tandem feeding. Keep your midwife in the loop as you go, especially if anything feels different in the pregnancy.