Need advice on weird periods

I have been ttc for 3 months now and my last 2 periods have been a bit funny.

I got my marina coil out 19/05/17 and got my first period in 10 years in June.

Current cycle I had bleeding on 15/09 enough that I needed to use my cup then nothing until 19/09 and it has been light to medium flow since.

My period before this was the same light flow for 2 days then nothing for 2 then medium flow for 5 days.

When should I log my period starting? Is the day before the gap spotting or is that my period?

I am so confused because it changed my fertile days?