If you can't shave your armpits for medical reasons, that is something a boyfriend needs to accept. You shouldn't have to make sacrifices that could cause you physical pain just to make him happy. I know you like him and all, but I would cut your losses now. He makes you feel bad about something you literally can't control, and he's trying to manipulate you into shaving so he's more comfortable, which is not a good sign; he could have other manipulative/emotionally abusive tendencies. And, in the grand scheme of things, you're still very young and seven months isn't a long time. I would tell him that it's your body and you get to make the decisions regarding what happens with it and if he doesn't like that, then leave.

On a seperate note, if you're not that fond of having hair under your arms and waxing is the only thing that doesn't trigger your problem, (but are worried about expense) I would look into the premade wax strips they carry at stores like Wal-Mart. They aren't that expensive and if you only need to wax once a month, one box will last you a while. It's basically a strip of wax that you heat up with a hairdryer (or rub it between your hands) and peel apart, and then apply to your underarm, wait, and tear off. I use them sometimes and have found them to work pretty well. Also, you could look into getting an epilator. It's basically a bunch of pairs of tweezers in a little machine that just pluck all the hairs out. It hurts a bit at first (but you get used to it, just like waxing), the machine is a little pricey (but you won't have to replace it if you invest in a good one), but it shouldn't trigger your symptoms since it's the same principle as waxing (although, I'm not medical expert, so take that with a grain of salt).

Anyway, I hope my advice helps you in some way, and good luck with everything! Feel free to message me if you need to.