Over 3 months of trying and still not pregnant... what gives?!

I'm just totally lost.... I got pregnant a little over 4 years ago with my son, he was not planned, we weren't having sex HARDLY at all, and we're using the pull out method... I figured this time of trying it would be so easy... I'm worried how long it's going to really take.. I'm 28 and wondering if that's why? I feel like I waisted too long to go for our second... and now I've screwed my self... I feel like my kids won't be close because of the age gap. I tried using preseed this month. Didn't work.... wondering if maybe there is something wrong with me now?