40 and TTC

I'm 40 yrs old...I have one 4 1/2 yr old girl already (which took a over a year to have her) and we've been trying for our second one for two years now. I have been diagnosed with POCS. My FSH levels are 5 (from a previous test) but I am overweight (yet I was over weight with the first.). I've been on Metformin (1500) for 4 weeks. I'm sick as a dog some days with bathroom problems. But I have to admit that the Metformin has helped get me to two bars on my fertility monitor (but I never reached 3.) and I have had sex before ovulation day and after. I have had all the blood work done, semen checked and have one last test to do which is injecting a dye to check that my tubes are open. Here's where the problem is...I didn't get my period this month as expected. I've never missed a period in my entire life unless I was pregnant. I've tested for pregnancy and three tests on three different days came up neg. I've had some pain on the right side here and there but otherwise my lower area feels really, really bloated. So I called my doctor and he's prescribing a med that would bring on my period but asked am I sure I'm not pregnant. I know my body and I'm not. So why haven't I gotten my period? He thinks there may be a cyst on my ovary on the right side. But why would that stop my period from coming? I'm dying to get this darn dye test done so that I can have my consult about all the test results to figure out what exactly is going on and to start the next step with injections (due to my age). It's aggravating and yet frustrating. Any comments, helpful tips and answers would greatly be appreciated.