Help -thin lining when periods due

My periods irregular due to coming of depo in July went to my first apointment for

IUI

and she said my lining is very thin for were I am in my cycle that the dr will talk to me about it. I don’t see him till Friday so obcourse I came home and googled it says thin lining can cause miscarriage if you get pregnant is this true ???

I had two kids the first after depo I assume my lining was fine because I carried fine so can something else cause this. ??

Can I still have

IUI

??

What causes this ?

Has anyone else had this ?

Anything I can do to fix it ?

Thanks I’m just worried

Last period 22nd December..