should I start again?

so my baby was born March 10th I decided I wanted to breast feed and do formula. I have inverted nipples so he wouldn't latch. Luckily I bought a nipple shield the shield was to big so he didn't latch I felt horrible. Hours later I got help from a nurse she brung different shields. So I pumped and also put him on the breast. 3 days later my breast were engorged and I couldn't do it anymore it hurt and I kept massaging doing everything I pumped a little every 4 hours or so but the engorgment wouldn't go down. Day 5 my son had a sezuire they diagnosed him with 5 day of life fits which is normal but they kept him for 3 days in the children's hospital I was told to not feed him the first day. My husband wanted to stay overnight with him so I went home with our oldest. Came the next morning and my son was on formula he was hooked up to all these machines so I stopped the breast feeding :( I eventually dried out. He's now a month and I've been noticing on my left breast milk still in there. So I squeezed and pumped and I made an ounce. I don't know if I should try again will it upset his stomach?