Panicing...need you to give your ideas on what this is!

I gave up trying to concieve. I flat out couldn't deal with it emotionally - it was all consuming and I just grew tired of it and decided it was God's will etc. So Im trying to get my plastics surgery scheduled and paid for by the insurance etc. (remember I lost 127lbs).

Now....I had sex with hubby January 28th, 29th, 30th and then he had gallbladder surgery. I THINK my last period was Jan 11th or very near to that. I wasn't paying great attention as I was not trying to get pregnant. That would put me having unprotected sex at around 14 days.

I am starting to panic yall. Because Tuesday I started feeling that "Im gonna start feeling" and then checked my CM and found that it was creamy and had a glob of brown (old blood) yet...snotty cm. I thought for sure I was going to start that night......
So then nothing AT ALL happened that morning following. I checked - there was nothing to be found.I had to pick up blood work from the doc yesterday so I had them run a quickie urine test with SMU...neg - but we didn't really let it sit for more than a couple minutes... I got a another smallish brown last night....NOTHING this morning. still got that Im gonna start feeling.

Is it possible I can still be pregnant even though that test was negative at 13 dpo? Shouldn't it show up by now?