Still confused whether or not I'm pregnant?

Okay so I have had a couple of BFP's and BFN's but still getting a monthly cycle even though it keeps coming late 
I bought a Doppler when I got my frist positive and actually used it today and I can't find the heartbeat yet but there were whooshing sounds and howling winds sound and also like crashing waves and I also found my own heartbeat 
I question is even if your not pregnant can you get there sounds because I heard it could be the placenta giving off those sounds but then my friend said it was my digestion track so no I'm not pregnancy 
So confused right now I have loads of pregnancy symptoms and would be around 12 weeks if I am 
Edit: I came on my 'monthly cycle' yesterday and today it's mainly been watery discharge mixed with blood - this is not like me at all 
What do you all think ?