There's 13 months between DS1 and DD - when I found out I was expecting again I was utterly shocked not least as we had tried for ages to have DS1 and only found out I was having him 2 weeks before starting IVF.
I also felt a bit embarrassed telling people tbh and it was hard work having 2 so close together - I was 34 when DD was born and I think it is a bit harder if you're older.
You can carry on bfding but they encouraged me to stop when DS1 was about 7 months because it does deplete your iron stores so it can leave you anaemic. I was also told to take care of my joints because the hormone relaxin takes about 9 months (I think - or was it a year) to leave your system but if you're pregnant again you get a double dose.
I do think though there are more pluses than minuses. The real upside is how close the kids are. The first year was difficult but after that in some ways I think it was easier because they could do so much together. It can't have been all bad either because we've gone on to have more kids, although I wouldn't actively plan to have two so close together again.
DS2 was born when DD was 2.5 and although I think it was physically easier having a longer gap between pregnancies, I found the age gap harder as DD felt more displaced than DS1 had done. Sadly we lost DS3 last year when I was 21 weeks pregnant but we're expecting DC4 this week (DS2 is 3 so again I'm expecting the transition for him to be harder than it was for DS1).
Good luck and try to enjoy it - sometimes life deals you an unexpected hand but, as unexpected hands go, this is a good one!