Bleeding in 3rd trimester

I am pregnant with my first via IVF...I actually bleed on my 6th and 10th weeks of pregnancy...but my second trimester was so good...but again when my 3rd trimester started I had heavy bleeding with blood clots on week 28..

I immediately went to hospital...but they couldn't find why...my cervix was closed..I don't have placenta previa or placental abruption...I took ecoaspirin and my doctor told me to stop that...I took injection to stop the bleeding...it's almost a week now..my bleeding has stopped...anyone experience like this...I want to make it upto term...any suggestions???