My periods after baby are much different than before- they still are after 4 years. I used to have zero cramping or other symptoms and was regular down to the hour. After baby, my period has a 3-5 day window during which it may appear, with a couple times of it being up to 2 weeks late. (Which had me really freaked out, lol.) I all so get cramping, headaches, mood swings, and breast tenderness when I'm PMSing. And yes, I noticed a HUGE difference in the discharge.
For what it's worth, I have gotten myself worked up about the possibility of being pregnant several times in the last few years. Having a wonky period sucks! Lol. When I was nursing, I was on the mini-pill for a few months, but hormonal birth control messes with my system horribly so it really wasn't the best option for me.
You can get a period tracker app, and it will give you a better idea of what is going on. Mine is fairly accurate, and I usually start my period within 2-3 days of the projected start date. (Like I said, I'm very irregular so that's actually pretty good... Pre-pregnancy, the app tracked it perfectly.) it also tells you when your "fertile" timeframe each month is, and your ovulation date, so you can be extra-careful during that time. (This is referred to as the rhythm method of birth control.) it's definitely an imperfect system, but along with condoms will give you a little extra peace of mind.