Our future

So my boyfriend and I have been together almost a year, so weve discussed certain things like marriage and having children, but hes expressed to me that hed be worried for me when I do get pregnant because I'm very small. Hes worried I wouldn't be able to handle pregnancy. I'm 5ft4 and I weigh 97 pounds. I dont have an eating disorder or anything like that, I've just always been small. Would I possibly have a hard time going through a pregnancy? Gaining enough weight for it? The last thing I want to do is disappoint him. We're not planning on having kids yet lmao, we're only 20, but in the future.