Early pregnancy u/s showed gestational sac of 5 wks 3days, went to the er 6 days later and nothing found in my uterus

So i got the implanon implant removed in March 2011 and had one normal period the 1st of June then the 14th July i had a really light period, The dr sent me for an u/s to see what was going on and a blood pregnancy test which was negative. A week and a half later I took a HPT which was positive because it was a Friday i went to the DR on the Monday and sge ordered another u/s which showed a gestational sac measuring 5wks 3days which didn't sound right to me. I had blood taken and it matched what the u/s was saying. Well 6 days after the u/s i went to the ER because of cramping on my right side. They took more blood and sent me for another u/s where they couldn't find anything in my uterus or even my tubes. My HCG levels had risen but not doubled, The dr said it was fine because they went up by 70% well that was on a monday. The Wednesday the hospital took more blood and called me on Thursday morning to go back in, A different DR seen me and said my levels had risen again by 70% but he wanted another u/s. When i got down to the u/s they told me because it had only been a couple of days since my last one they wouldn't see anything different and that i should wait a week and come back because they thought i wasn't as far as i thought i was. I go back to my ward and wait for the DR who comes in to tell me the u/s showed nothing again and that it was most likely ectopic. He told me to take an Injection over surgery so i panicked and said ok i will have it. He gave me the injection and sent me home. Well it's been 4 days and i had my first blood test to see if the pregnancy is ending. I still haven't had any bleeding and only small twinges of pain all over. I feel so guilty and sad that i took the injection instead of waiting a week but then i look at my 3 year old and know waiting a week could  have been too late and that may have left her without a mummy. But now i feel so scared that it may still rupture while i'm sleeping or home alone with her. Does this ever get easier? I'm so lost as to how this happened. I tried to explain to the the DR on thursday that i had the same pain with my daughter when i was 7wks but he just didn't want to hear it. Anyone who has been thru this would be great to hear from. And how future pregnancy went for you.. Thanks