Clicking noise/feeling from bottom bracket/pedals/chain?

[saashi]

Hey, lately I have been noticing an extremely annoying clicking/grinding when I am pedalling - it's mostly that I can feel it in my feet, but if it's pretty quiet around I can hear it as well. It's very inconsistent - sometimes I hear it very often, then I could go a minute or so without hearing it. I feel it in both feet, sometimes together and sometimes one at a time, but more frequently on my drive side. Generally, it's worse when putting more pressure on the pedals.
I really thought it was my bottom bracket, because there is an opening at the bottom of my frame under the bottom bracket, so dirt can get in there when I'm pedalling. So I thought that was what was causing it, especially as it is noticeably worse in the rain. But I just replaced my bottom bracket with a cartridge/sealed bottom bracket and the noise is still there. I tried replacing the pedals today as well, and that didn't help - though the pair I replaced them with is also very old..
I ride a fixed gear if that's helpful. Any ideas what else it could be? It's driving me crazy!! Thanks!

[GeorgeET]

Only thing left is the hub or the chain. Have you serviced them lately.

[ajstevo]

Check the chain carefully for a stiff link. As you don't have a rear mech you wouldn't get the noise thru it. Any damage to the chainring?