If you want a good place to start for a good general plan to get better, check out the protocol:
Life isn’t that bad using condoms…so consider switching to those instead. I wouldn’t be too worried about spreading candida orally because everyone has it in their bodies, just at different levels. Same with parasites. We all have bugs, and all it takes is a long term healthy diet and a good general plan to get over them. If your bf has a suppressed immune system, it might not be a good idea to kiss a bunch because candida will only develop in the correct environment.
Consider consulting a naturopathic doctor for some good supplements from brands such as thorne, standard process, integrative thereaputics, etc. If you look at these product lines, I feel that a naturopath can heal anyone with what there is to choose from.