
!!Trigger Warning!!
I'm not sure I should be saying this but I find that a good place is under the breast area. So that way, if you're to have on a bra it is still not noticeable. Heck, if you're naked its not really noticeable unless you lift up your breast (and i'm not heavy chested). I do my upper upper thighs (short shorts usually hide them) but I can't gaurantee your husband won't see that. I have done the inside of my upper arm - the underarm would be a really good place but probably uncomfortable. There's also the bottom of the feet (which i've done; not a fan of) and elbows that people don't usually look at.
I've burned my hand "accidentally" with a glue gun - I find that using objects that make sense are easier to be honest about without a million questions. Also, I would consider less scarring things; I find that pricking with the diabetic needles helps with me because they hurt, bleed a good bit but leave almost no scar and really are a safe alternative to more drastic measures of self harm.
My career and life circumstances don't allow me freedom to "not care" about these things so i've learned a few tricks. These tricks, as a result, keep the harm controlled and with little risk of accidents or infection.
Of course, stopping all together would really just completely fix the problem.