Negative tests but I have a bump now??

This is going to be quite long, so please stay put:

I have taken five urine tests using only morning pee: all negative. I’ve been to the emergency room twice because about three weeks ago I began having some bad pain in my lower abdomen and it wasn’t just in one area, it was all over the place. It felt as if something was pushing whatever it was that’s in my stomach upwards, because soon I had this bump right below my ribcage and above my waist. Of course, they didn’t know what was causing the pain, so they just passed it off as constipation. I have been having some constipation, but it’s not chronic; I have never had this type of pain. I even told them them that I thought I was pregnant, but they really didn’t do much about it. The only test they gave me was a full blood count because they thought I could be anemic. Right now I would be about, thirteen weeks pregnant, if that was the case(hopefully it’s not). I’m now noticing a small bump, noticeable because of my weight (I lost weight for unknown reasons and now I’m 100 pounds). I’ve read online that if you tuck in your stomach, and if small bump is still there, there’s a chance your pregnant. Not only is that true to ME, but my stomach has been feeling very firm and slightly round too. And I know I sound like I’m exaggerating a bit, but ever since I realized that I could be pregnant (with the first change being in my nipples) I have been keeping track of my weight, my symptoms, but not obsessively. I have found that most symptoms have matched up to me being “pregnant”. But I’m on the implant, and I have been bleeding for over thirty days now, like a light period, which I thought was the reason, but it’s probably not. So, if anyone knows why my tests keep coming out negative or why my stomach is getting a little round for any reason other than pregnancy, please do explain because I’m really worried, and no matter how much I explain to the doctors that I may be pregnant, they just won’t really listen. I have been taking antacids though, because they thought it had something to do with my urine. I have a follow up appointment on the 29th of this month, and hopefully they’ll give me a pregnancy blood test this time.