Question regarding pumping

jsprague2

My LO is 4 months old, and I would call my supply well established. I'm a SAHM so I don't normally pump, just enough to have a little stash in the freezer.  I haven't pumped in probably about a month, but tried last night and got less than an ounce. Same thing this morning. I also just started the mini-pill last week. 

 I had issues with OS at the beginning, so this is all new to me.  I started eating oatmeal every day and I've been trying to choke down Mother's Milk tea, plus I'm going to stop taking the pill and see if that gets me anywhere.  

My question is, am I unable to pump anything because my supply is established and my body is just not producing any "extra" or should I be concerned that my supply is dropping, either naturally or because of the pill? I thought the mini-pill had no effect on milk supply, but apparently there's a small number of women who report a decrease.  

TIA!