There is a big differance in taste & texture of breastmilk & formula... so some kids have issues with it. Also, one of my sons had really bad gas from formula, but no issues w/ breastmilk. We had to use tummy gas drops on him... which helped greatly and then he started eating a bit more formula.
As for weaning... it took me about 2 months to wean my last. I dropped a mid-day nurse/pump section at a time. Wait about 5 days for your body to adjust and then drop the next. The 2 hardest to stop were the first & last ones of the day... which we the last 2 we got rid of.
I do understand the blocked ducks... they are very painful & I've been told the only way to help them is to have the baby nurse more often w/ the chin where the blocked duck is. Mine were always on the underside of my breast - which ment that I had to lay in bed with my little guy laying parallel to me (which was my least fav position). So, they kinda hinder the weaning process.
To be honest - nursed babies sometimes only take a few oz of formula. Since it is thinker & fills them up quicker the breastmilk. As long as they are not hungery right away & are having the correct # of wet diapers you should be fine. In time he will start drinking a little more formula - that is after he gets use to it. Also, maybe try to feed him before he is super hungry... since babies are moer likely to try new things when they aren't completely hungery (they have more patients then).
As to feeling guilty - I did with all of them when I weaned them... the last was 10 mo old when he weaned. But something I did do was hold him close when I gave him a bottle as well. That way he still got the close cuddling holds he was use to w/ nursing, but now he got to look me in the eyes more. But also, sometimes it is easier for other people to first start the bottle routen... since they will sometimes wait for mom to give in. And if they can see, smell or hear you - they will wait... so if someone can help to begin with it might make it a little easier.
Sorry that you are having issues with your health, but you are doing the right thing!!! You are truely protecting your child & doing the best that you can for him... which shows that you love your child. Please take care of yourself & your little one! I hope everything works out for you and your son!!