Strange period question

[scsigrl]

For the past 3 or 4 months, every month, things are strange.

I have PMS, I have some spotting (heavy enough to use something) then NOTHING. 2 days later I get my period doe real.  Any ideas what would be cause this as an ongoing thing?  I didn't think anything of it at first but now that it keeps happening I am wondering if it is something to worry about.

Any help is appreciated!  TIA!