Pregnancy symptoms??

I am 35 with a 19 month old son, and I am currently on the pill. I do miss some of the pills a couple of times a month. I missed my period, was supposed to start the 5th, and never came. I have also been very gassy and nausea, and had some minimal breast tenderness last week. I have also been tired but i am not sure if thats just from raising a toddler in general. I took two tests last week, and they both came back negative. Any advice would be appreciated. I have also been really achy the last few days.