Think I'm pregnant after only one month coming off BCP and just gave birth to baby girl Oct 1st, it is possible for this to happen so fast?!?!

Devin
Hi my name is Devin, I'm 35 and I just gave birth to a beautiful baby girl Oct 1st 2015. I was on the pill from time I gave birth til Jan 26, my last period was Jan 22.....its now March 1st n no period! According to this app, I'm 5weeks 3days pregnant, I have not taking a HTP but I do feel like I'm pregnant, sleepy, crying over every little thing (even commercials, lol), and other things that are associated with pregnancy. We do want another one and that's why I stopped taking my birth control but I didn't think it would happen so fast, now this morning I woke up to having very very lite brown discharge or spotting and I'm freaking out!! Could I be miscarrying or was I even pregnant even thou in my heart I believe I am....this will be my 4th baby, I have an 18year old, 12year old, n 5 month old so I pretty much know what to except but I am older now n with not even having one regular cycle before this happening I don't know if it's even possible to be pregnant if it's all in my head or what! I want to be now that for the past week I've believed I was, if I found out I'm not I'm going to be so upset....has anyone else gotten pregnant so fast after coming off bcp and what should I think about this brown stuff??? Any advice, help, or thoughts are appreciated.... Thank you all for your time!