Sweetie, ((((hug))) I know how you feel, I had a m/c last summer that started with spotting, and yesterday at 4 weeks pg I started to have spotting so I thought this one is probably "over" too..I feel much better after talking to the nurse, she said around 4 weeks the spotting is most likely still implantation bleeding and it's very normal to have a little spotting when you miss your period, especially if it's not accompanied by severe cramping or if the bleeding doesn't catch up..You're 4 weeks yourself, I would think and hope that your spotting has the same reason...!
I think there's a great big chance for this one to stick, don't give up the hope yet, I know it's easier said than done but we have no choice but to keep our spirits up..You could ask your ob/nurse to check your hcg levels, until it's high enough to perform an ultrasound.....I know hcg levels alone won't tell much because the ranges are so wide, but it shows a tendency..raising or falling..doubling normally, or not..etc..it could give you a better idea of what's going on so you don't go crazy while waiting for the ultrasound..I got my ob put in labs for me based on my worries and past history of losses and anxiously awaiting for the results today...good luck to you!!!!!!!!!!!! Sending many sticky vibes!!