Just read this whole thread, because not been on here alot recently, so thought i'd get back up to date! Stu that post was very sweet and welcome to PF. Ema - Lou is there anyway you can speak to the gp you saw or get another appointment and insist on blood tests. In answer to your question, no i don't believe you'd be able to tell from an internal examination whether your pregnant or not, and the fact she couldn't find your womb doesn't instill the greatest confidence in her ability.
A scan may not have shown anything either, and it could be possible as been said before that you HCG level is just low, doesn't really mean anything as everyone's different. But a blood test is worth a go. I'm trying to think of ways you can get an answer asap, would you be willing to call the hospital and complain to someone senior about the treatment you recieved and how its left you feeling? Big hugs to you both, I really feel for you both and am keeping everything crossed for a good outcome xx