My boyfriend [25m] has a much higher libido than I do [24f].

To get straight to the point, my boyfriend (25) has a very high libido, while I (24) have a much lower one. This has been the only source of conflict in our five-year relationship. He’s always ready for sex and feels frustrated if it's been 3 to 5 days since we last were intimate, while I can comfortably go for months without it. We’ve talked extensively about our differences, but we end up going in circles, both understanding that neither of us is at fault—this is simply how we are. We've tried incorporating toys, explored new kinks and fetishes, and even considered an open relationship, but he hasn’t found anyone yet. We went to couples therapy, but the therapist stopped seeing us, saying we were "the most healthy couple she's ever seen." Both of us have done individual therapy as well, but while it provided some temporary relief, it hasn’t led to lasting solutions. I can't use sexual stimulants because I have a gene that could trigger certain cancers. We feel like we’re at our wit's end; we want to get married, but not if we’re going to spend our lives struggling with this emotional issue regarding sex. I feel like I’m living the dream—he's the most understanding and amazing partner I've ever had, my other half, and we don’t want to lose each other over this. I would appreciate any advice, if there’s any to offer at this stage.