My baby is not gaining weight

Hi my baby is 12 weeks old. She was born with a weight of 7lbs 4oz.. At first i decided to completely breasfeed her but my milk is not coming enough for her.. I tried different herbal stuffs even prescription medications to increase breastmilk (domperidone).. She is always hungry so we decided to breastfeed and bottle feed her.. At first it was going along well and is gaining right but at age 6weeks she had nipple confusion and would only latch on my breast and not on the bottle anymore.. By 8weeks she weighed 10lbs 10oz.. 3weeks later i weighed her again she lost weight, she only weighed 10lbs 5.5oz.. And 1 week after that she weighed 10lbs 6.3oz which is less than an once.. We have tried different kinds of nipple for the bottle different formula but she still doesnt like it.. I also pump and would offer breastmilk in the bottle but she still wont take it.. What should i do??? Please help me.. Im getting frustrated and worried about my baby..

[Renee Radenberg]

Have you tried the nipples that are similar to the breast? That may help. Try to feed her via bottle ½ formula and ½ breast milk mixed together, at all feeds, to help prevent confusion and/or rejection. She is 3 months old and you can start her on infant cereal (1-2 Tablespoons mixed with formula) twice a day for additional calories so she does not lose weight. Hoped this helped you.