D.W.
There is nothing wrong with what you are doing. Please don't let anyone tell you that mom can't be used as a pacifier with a 3 month old breastfed baby! A 3 month old is not ready to self-soothe and she may not be ready to sleep thru the night.
Breastfed babies do just fine with side lying nursing usually.
And do not give her a soft blankie! That will increase her SIDS risk! No blankets, pillows, toys. But you already know that mom!
I believe that foremilk can cause some gas issues. What I would try is don't immediately jump to giving her the breast when she stirs. My oldest would wake and scream for about 20-30 seconds and then pass right back out! I learned this one night when I didn't get to him fast enough. It was just part of his normal sleep pattern that we all have. We all have different levels of sleep thru the night time.
You might also go back to the prenatals that you were taking that didn't seem to bother her.
When you do begin to teach her how to sleep I highly recommend Dr. Sears Baby Sleep book, The baby whisperer and the no-cry sleep solution. Life savers for me! I used info, tips and tricks from each of the books to formulate a sleep plan for my babies.
I breastfed both of mine exclusively, nursed both of them to sleep or rocked them to sleep, held them till they were completely asleep-basically all the things you get told not to do and I had one champ sleeper and one pretty good sleeper!