I've had a unprotected sex around 17 days ago and my period is not here yet. My last few months period is irregular and would even miss a month and eventually came on the early days of 2nd month. Is there chance that I might be pregnant?

Yes, when you have any sex it is possible, when you have unprotected sex, there is a bigger chance of pregnancy.

I would wait perhaps another two weeks and if no period comes try a HPT

I've had a unprotected sex around 17 days ago .... Is there chance that I might be pregnant?

Is this a serious question? Of course there's a chance.