Feeling a little down today

So we want our kids to be close in age so we have basically been trying for another since baby girl was born and we have been having a lot of sex since getting the go ahead and yet NOTHING .... it's so frustrating... especially since my mother in law and sister in law love telling me how once they had there first kids they were so fertile and only had to have sex once and came out prego with their second children so they can't understand why I'm not getting pregnant .... I had hope this month since AF didn't show up but I just took a dollar store test and yet again NOTHING .... I'm just hoping it happens soon or at all at least ... it took a while with my first so fingers crossed!