I feel like I'm being selfish (longish story)

I have wanted to breastfeed before becoming pregnant . I knew that it would be one of the best choices to make for me and baby. However I recently chose against it. I've decided instead i would formula feed so that I can go back on my medication. 

Prior to pregnancy , a few years back actually, I have been diagnosed with bipolar disorder , depression, severe anxiety , and mood disorders. It had gotten to the point where I didn't want to live. I'd spend all my time drinking , drugs and not wanting to be here. I barely worked or even took care of myself. My fiancée helped a lot! He got me out of the self loathing stages and I stopped doing drugs but I still drank a lot. 

I eventually seen a doctor who began prescribing me medication that helped me so much. I had a better outlook on life. The only problem is we didn't realize how fatal it would be for our baby. I was pregnant prior to this pregnant and the medication instantly caused a miscarriage. I eventually weened off of it. And became pregnant again. Now being off my meds for six months has been extremely hard. I meditate and I would never resort it self medication in any way. But I feel like I am being so very selfish to this child by choosing to go back on my meds after my pregnancy instead of breastfeeding her.

What would someone do in this situation? I know my mind and my feelings and I've thought long and hard about this decision . I'd just like to get others perspectives.

If your goal is to be mean please don't respond.