5 weeks and 3 days pregnant and bleeding off and on

Hi everyone

I just wanted some advice im now 5 weeks and 3 days pregnant and im bleeding off and ok dark red and brown only when i go to the toilet and wipe , the bleeding stops and starts again i am not having no pains along with it ive has blood test done and my hcg levels are always doubling and i have done a few ultasounds and this week they saw the gestational sac and the yolk sac but still no embryo is this all normal? as im really worried:(

thanks