Thick uterine lining but no sack seen in the ultrasound

Okay ladies well as of today I'm 11 days late for AF and I've been having all kinds of symptoms like my boobs hurt Peeing all the time throwing up nauseous tired all the time headachessinus congestion that I just can't shakePulling pain on the one side And much more....Anyways I made an appointment for my obstetrician to check me out because I want to know what was going on because I also have had to think positive and one definite positive... So I went for an appointment yesterday and the doctor said that I was definitely pregnant based on my last period And all the symptoms that I was having so she sent me for an ultrasound so I went to the ultrasound the same day and the tech said that based on the internal that they did because They didn't see anything on the over the belly ultrasound with the internal she said all she saw was a very thick uterine lining that is good because that's the first sign of a Pregnancy but she said that I was definitely not as far along as I thought I was because I thought I was only seven weeks and a few days and she said based on what the ultrasound said I would be around four or five weeks and with the ultrasound machine it can't pick up a baby when there that small so she said not to be discouraged that most likely I'm definitely pregnant but I'm going in for a blood test ..... So my questions for you ladies are have any of you guys had the same thing where you had to thickened lining and then you went back in a few weeks and you were definitely pregnant .... I don't know whether to be scared or to be excited but I definitely feel pregnant.... Please help