In law issues

I'm 18 and 23 weeks and 5 days. And my boyfriend is 24 I've been with him since I was 16 he lived in South Carolina and I lived in Florida he would come down and see me I lost my v to him then I got pregnant (after a year) I wouldn't have sex till I was about to turn 18 and now here we are almost two years later I'm turning 19 August and my son will be here November we decided it's time to get married we now live together I left Florida to be with him awhile back and his family is so agents us getting married saying we are to young to make decisions...he has a great job he makes 24 an hour as a welder and we keep up with everything and never fall behind. And we know we love each other but now his family will not talk to him because of this but my family is supportive? And I'm not understand why it's such a big deal when his grandmother told me they got married even younger then what we was