quite worried

Abigail
Basically I had a baby nearly 5 months ago and my periods have been really heavy (sorry if tmi) and been having about two a month. This month I'm pretty sure I haven't had one :/ but had period like pains and maybe a small amount of spotting. I'm on bc and not very intimate with my partner anyway. 
I'm freaking out that I could be pregnant again as we always try and me so carful. 
Anyone else had this and not been pregnant? 
Thanks in advance