You wear a sports bra to bed? They say its not good for developing breasts (whoever they are) but I imagine it would be restrictive. I have a size 34 sports bra and its okay, but it's loose around the band and pushes my boobs up. If you need to wear something to sleep, get a cloth cami bra. I have tow from Bollovo: one in light pink and the other in baby blue. But that might be hard to find. Victoria's Secret has Secret Cami Sports bra which is like a sports bra but with adjustable straps and a nice soft cotton so it's more cloth cami than sports bra. I'm a 32C so it's hard to find bras in my size. I'm usually a 32D. Guys seem to really like them lol but srsly, I'd try it. If you're over a B cup, I would just by regular bras. Even an A but that might be more juniorish. Not all women have big boobs and really it gets on your nerves when people comment on your "nice tits" all the time.
If you have boobs, why not go full-time? You'll have to soon anyway. The sooner the better. I went full-time in three months. Just wondering, so if you'e not ready then def don't as it could just be a bad experience.
EDIT: You've been on HRT for almost two years and you're not full-time. I've been on it for 15 months and I'm full-time no matter what. But I love being full time, I went to NYC and wore these purple-bluish skinny jeans from Sample with holes in the knees and now in the thigh cause I have big fat thighs and this cute form-fiting striped top and just basic flats, and I felt great. Plus, I bought this Nala Ross brown leather Hobo bag from Urban Outfitters and it effing rocks. Tottaly completes my outfit with my necklace ring braclets and watch. I neeed my ears pierced tho so I can start wearing hoops. Tangent sorry. So, really, consider going full-time, what's stopping you? it could be the BEST DECISION eva, like OMG!!!!!