TTC #2 - any advice on fertility after #1?

I have been ttc #2 for about 4 months now. My husband travels a lot so I'm not sure if it's because we're missing the moment or if it's something else. I should also mention that I still bf my DS who is 20 months just in the morning. I have been marking my cycles and they are all over the place! First was 36, then 38, 32 and 28. This last cycle I use OPKs and it showed ovulation on day 19 and then I got my period 9 days later which I know is too short but I don't know if that's typical for me or not. Now I'm taking pre-natals, b6 and vitex supplements to try to regulate. I didn't get my period back until around June, when DS was 16 months or so. Does anyone have any advice to share about their fertility after children? Thank you!