If you're on facebook, I would suggest seaching for the Ectopic Pregnancy Support Group - they are really helpful with lots of people having shared experiences or knowledge they are happy to share.
I would say if your HCG is rising well, it's less likely to be ectopic, but they are unfortunately right - if they can't see anything, it could be you are further behind than you thought or it's ectopic or miscarriage.
I had an ectopic, which was not picked up until it ruptured so I can't tell you what my HCG levels were as they weren't monitored. I would say be conscious of how your body feels - although my pain wasn't really one sided, I was incredibly bloated and everything in my abdomen felt quite squashed together. I suffered from bowel pain/pressure a lot, which is quite common along with just a really crampy tummy. Given what you've described above, if you don't feel right in any way, push to be seen.
I so get feeling emotionally drained - I had 2.5 weeks of bleeding, being fobbed off and told I was miscarrying, so I actually felt numb that it ended up surgery and a pregnancy loss as I was just relieved to have an answer and not feel so ill. (Be prepared for medical staff to be clinical/not especially compassionate... I was shocked by how they just told me it how it is, with no regard given to my mental wellbeing.)
But, ectopic pregnancy is not the end of the world. I had a salpingectomy (removal of one tube), but fell pregnant again very quickly, so there is hope after healing xxx