Advice?

So me and my BF been dating since November and things have progressed really fast feels like forever... Anywho... We always talked about having another child together he has a 5 yo i have a 9 yo from previous relationships/marriage... I’m 28 hes 36... i think that I’m pregnant of course haven’t been trying but also not preventing and we have had sex 3 times in my window... I know i want another child but could it also cause a strain because our relationship is so new? I’m just confused