finally letting go and now possibly pregnant?

I decided to stop trying and try to regroup after becoming depressed. We went to Mexico and my cycles became irregular. We finally decided to adopt shortly after coming home. Now my cycles are regular again and while we aren't charting or anything, we are still "trying". This month we had sex 5 days during what I considered my fertile window (based off cm). I then had brownish spotting for 2 days. Too light to even use anything but a panty liner. I just figured it wasn't our time again. That was around cd15. Now here we are on cd 28 and still no period. A small part of me is really hoping I'm pregnant but I don't want to get my hopes up.

When is too soon to test?