I'm a them, not a ma'am.

. Thanks for the apology there. Indeed, we're all humans.
I feel like going in in a disguise is more likely to draw attention to you than just going in as yourself, honestly. So often. when you work retail, you are so checked out, you'd be amazed at what you don't notice. I don't see how using contraception ruins a families reputation, but I do understand that you want privacy and it also sounds like you're concerned about your family finding out. That given, that's something else I want to mention.
If you are also sneaking around to have sex, and having sex in a "spot" -- somewhere that sounds like it isn't a place where either of you live, so isn't actually your property, you're taking an awful lot of risks, especially as someone under the age of consent in your state. You don't have to be over the age of consent to
buy condoms, but you do have to be over it in order to lawfully do the things that involve using them. Looking at the law in MS, it looks like if your partner is two years older than you, sex between you won't be lawful. I don't know your situation, so I'm just filling you in. Sex in public places is almost always outside the bounds of the law, as well as being often unsafe.
Sounds like you have a lot of limitations around things like online orders and other ways of accessing condoms. You said your boyfriend does, too? Can we talk for a sec about the notion that perhaps you two just aren't ready for all this given your limited access to so many basic needs for things here: to sexual healthcare, to safe and private space, to condoms and contraception, etc?