You'd have to come off T to get pregnant. Although T doesn't make you completely unable to get pregnant after a good amount of time on T you'd have to come off it to get that process working again, assuming it would work again (not guaranteed). And you wouldn't want to try getting pregnant while on T because it would harm the fetus right from the get go (and after 3-4 years, it's unlikely you would get pregnant while on T, though not impossible). So you'd have to come off T for a bit to get T out of your system and back down to female levels, then try and try in hopes that you will actually get pregnant, and only then do you get to a more known time of "only 9 months" on top of however long it took to get to the pregnancy stage.
You'd look like a pregnant man but be on more female hormones than you've ever been your whole life. Anyone with body dysphoria, when combining that with heightened emotions from increased female hormones, it's going to be an extremely tough time. I'd say you'd be looking at 12 months but with a good chance of more without T.
Also 3-4 years on T, you'd normally be looking to have had a hysto by that point. There's no firm evidence that it's 100% necessary but it is possible for higher potential of issues in this area when on T. Depending on where you live, it may mean you have to remain with female identity/birth certificate during all this time.
With regards to C section, yeah, you can plan ahead and so on but there's plenty of occasions where C section is planned and then it doesn't quite go that way and there's not enough time. So even if you plan for it, you'd also have to accept that problems can happen and you might not have a choice in the matter. Following pregnancy it's not definite that the skin will tighten up again in the gut. Some end up with cellulite for life. Also, there's more risks to the baby delivering by elective C section compared to natural.
For freezing eggs you can be talking up to $30,000 per egg! If you have that kinda of money, go ahead but it's absolutely not cheap!
As for chest - you put on weight when caring for a baby and would go back to female fat distribution which means your chest may grow a little. But they wouldn't swell because that's all about breast tissue and you'd have very little of that left after surgery. Your hips and butt, however, would gain fat again and probably quite a fair bit which will be hard to shift. You will also likely gain subcutaneous fat in your skin again and that may make your features less masculine, i.e. chubbier, rounder cheeks.
Also worth noting that any muscle you gained on T, you'd likely lose a lot of it in the same way MTFs lose muscle mass when they start HRT.
You're free to do whatever you like. Personally, I can't understand why any man would want to get pregnant, because only female bodies (what you chemically go back to if you stop T) can get pregnant, and at that point, in terms of hormones, it's like female times a million! Basically you have to ask yourself if you're dysphoric enough that you want a male body, are you strong enough to be more female than you've ever been for a year+? Is your particular gene pool that amazing that you personally have to be a part of the baby? Plenty of folks here can absolutely state that blood doesn't make a strong family. There's many of us who have supportive parents but a lot of us who have families that don't stand by them or support us. You and your BF are essentially a gay couple right now, any other non-trans gay couple would have to adopt or use a surrogate. Do you need to carry the child yourself in order to have a family?
Also, as someone who was adopted to a family with kids who were the "real" kids, I'd advise against having one "real" kid and others adopted tbh. I use that terminology because that's what siblings will use in fights. No matter how great you think you'll be as parents, adopted kids are likely to forever feel themselves secondary. Whenever something doesn't go their way they're going to jump right to it being because they're not your real kid. I've been there and I know a few other adopted kids who have felt the same way and rebelled far more strongly than kids who were adopted to families where it was just adopted kids, or just them. Don't get me wrong, it's better to be adopted than not, but if there was a choice between a family with no, or only adopted kids VS a family with a biological kid already, the first is far preferable in terms of environment and the child feeling better accepted as one of their own.
