confused

So today I am six weeks and six days. I had my doctors appointment and did an ultrasound transvaginal of course. He states that he thought what was a very faint that looked like a heartbeat. Because of my history of miscarriages it is hard for him to tell me if he is certain of what he sees. Levels are still going up I feel perfectly fine I have not been spotting bleeding no cramping no nothing. He basically told me it could still be too early and then we will not get a strong heartbeat until about eight weeks. Next week I follow up for another transvaginal ultrasound. Have anybody else ever heard of such a faint heartbeat?