YANBU at all. It's devastating to lose a baby, no matter how small, and even more devastating when you have to see pregnant women and babies everywhere. It's true that you're noticing them more because it's so much on your mind, but that doesn't help how you feel about it.
I had a MMC at 10 weeks last January. I had an ERPC and tried to get on with my life, including TTC again. In March I had a few serious bleeds and went to A+E as I thought I might be MC again. It turned out that the ERPC had not been fully successful and I had a collapse, emergency surgery, a blood transfusion and a 2-night stay in hospital. We hadn't told many people about the PG so I felt like I couldn't talk to anyone about the MC, except a couple of good friends. Those that had had children were really supportive but one who had not, whilst intially being very sympathetic, soon got bored of the fact that I didn't go back to my old self within a couple of months.
Not long after the 2nd ERPC, my stepsister announced that she was pregnant. My stepmother let me know in a really sensitive way but I was still devastated. I pretended to be ok on the phone as I didn't want her to feel bad about her PG, but once I hung up I started hyperventilating and had to sit down on the floor in the supermarket.
Plenty of people will think that you should get over it quickly as it wasn't a 'real' baby but they don't realise that you are mourning the life that you had dreamed of and had started planning as well as the baby. Some people told me "don't worry, MC is really common", and my MIL even said that she had probably had loads of MCs but she'd never made a fuss about it (she was basically saying that every late period is a MC). None of this was helpful.
You won't forget about this experience but time will make it bearable. Ignore anyone who implies that you should be over it already. You don't need to be made to feel bad about it and you definitely don't need to get into any arguments about your feelings. Previous posters are right - your DH is probably suffering too. My DH is really supportive but his approach to dealing with painful things is not to dwell on it, so he didn't want to talk about it much after the first week. Maybe try to find someone else who you can confide in - a good friend, or GP as has been suggested.
I also wanted to give you hope - I know you have to wait before TTC again, but you have conceived once and I'm sure you will again (I now have a 6 wk old DD).
Sending you big virtual hugs and wishing you all the best for your back treatment and TTC. It will get better.