It takes time to get pregnant. 4 months really isn't that long. Keep trying.

It took my friend just over 6 months- they were about to get fertillity treatment ( a bit soon, I thought) they just hasd a baby girl.
Sometimes people try too hard, only having sex around the day you are "supposed" to ovulate is, I think, one of the biggest mistakes people make (unless they are charting it with themometres maybe).
Not everyone ovulates on or even around day 14 of the cycle. The sleeping lump of a 6 month old here on my lap was concieved on day 6 of my cycle, last feb. We got married in dec. And spent jan "trying"- I was two weeks late, but not pregnant- so after that 6 weeks of pressure, I was over it. When my period ended, I just had sex wheneer we felt like it.
I concieved 2 days after my period ended. (the first time that month that we had sex)
if we'd "saved ourselves" till day 14, or even day 10, the boat would've already sailed long since.
Who knows how long we would hasve been trying for.
I gave this same advice to my friend, when she was trying so hard, I don't know if she changed what they were doimg or not - I just know it wasn't long afterwards that they gave us their good news.

I agree with el, I conceived 32 days after my last period. I thought I was about to start, now i'm 18 weeks and couldn't be happier.