is not normal sign of pregnancy, but not a very bad one too especially when you say your ultrasound is normal. Spotting , bleeding in early pregnancy may be signs of ongoing abortion but most of the spotting resolves on itself without heading to abortion especially when there are no bad signs on ultrasound like in your case.
Just get your ultrasound repeated after a month or sooner if you develop more pain or bleeding.
Susten is a progesterone
containing tablet. Progesterone helps in supporting early pregnancy and also relaxes the uterus thereby relieving your pain. There is no harm in taking susten though 100% advantages of its use are still to be proved.
Other measures you should take to ensure that your pregnancy safely continues are :
Folic acid tablet
regularly once a day 5mg tab
Adequate rest, hydration, sleep
Avoid sexual intercourse, heavy work, travelling.
by taking good amount of salads, fruits and vegetables in your meals.
Maintain personal and perineal hygiene. Use a pad till you have spotting to asses the amount of bleeding or discharge.
Donot take pain killers on your own for your abdominal pain
, see a doctor if its severe.