Ladies please need help

I am mother of 4 yrs baby girl.i am 34 now TTC (trying to conceive) for 2nd baby,Mine is 28days cycle and periods are regular. On June 7th I had period After 6 days had intercourse nearly after 2 to 3 days started backpain,cramping,heartburn and my cervical mucus is creamy white till next period.i got my period on July 5th on correct date but it lasts only 2 and half days(normal bleed)which usually lasts 4 days.5th days I saw thick brown spotting very very light on 3 to 5 spots.Again now cramping,tired,sleepy,little soreness in breast,back pain,all tests negative this didn't happen before with my 1st baby.so much confused.i didn't fine for blood test,For any one happened this before plz help