congratulations on your beautiful baby.
Sending hugs and sympathy your way.
I found this incredibly hard. For me, DD constantly lost weight, despite constant feeding and expressing. In the end we had to top up with formula and I did struggle on with mix feeding until 6 months. The BF group wouldn't come and help me because DD had been given formula!! 
I was absolutely devastated. For me it compounded my failures and I was also unwell with Ptsd and anxiety. DD was born after fifteen years of miscarriages and failures, I took the BF issues very, very badly.
I remember what you describe, not wanting to go out in case everyone was BF and I was judged. I tried to time things around her feeds so I could hide it. I would also use the ready made milk when out and about and told myself I would say it was expressed milk if asked, I was never asked.
Ultimately DD is happy, healthy and loved, that's all that matters.
The more I went out the more I realised lots of people formula feed lots mix feed, lots BF. I made good friends, I became the advice point as some slowly began to introduce a bottle as we reached weaning.
I never judged anyone who was formula feeding, yet felt I would be judged, silly eh?
I still use ready made out and about!
Enjoy your baby, seriously, nobody cares. They will all be worried about something, I actually found telling people how much it upset me was a good place to start. Everyone then confessed how bloody hard it is and how much pressure we all have in lots of areas. I still wish I could have BF, but it hasn't stopped me forming friendships and to be honest, if people did judge you, you don't want them as friends anyway.
Don't let it stop you, you will be fine.