Question: Baby not showing in Ultrasound

I went to doctor for check up when Im 1 month but doctor said no baby but my lining is thick. In my 2 months I visited another doctor but said "no baby found" so I waited another month. In my 5 months I can feel that something is moving inside my belly. Kicking, fluttering something like that. Baby's even response when I poke my belly so I visited another doctor again for Ultrasound. I myself sure that I have a baby but doctor said "There is no baby found" Imso worried because Im 5 months but still no baby found but I felt it and my belly is getting big. And can feel the baby's kicks.Im 6 months now but get bleeding this afternoon. Please help me.