Advice please

So I gave birth to my second baby on 18th may he wasn't meant to be due until 7th July, his older sister was also early. I bled after I had him for about 4 weeks then stopped experienced horrible period pain and started bleeding so it was obviously my 1st period it lasted quite long and was on and off until 10th of August. From about mid July until it ended it was a lot lighter so me and my partner did have sex a few times we didn't use protection. I still haven't gotten my period this month I have on and off cramps, some nausea, lower back/hip/leg pain, sore boobs, metallic taste and food tastes different and a few more symptoms. But because I didn't write down when m period started and ended it's making it quite hard to guess when I should test (both pregnancies couldn't find out until closer to 7 weeks or over) I feel like I am pregnant, I just need to know if I was pregnant how many weeks could I be and when should I test