Cycle disappearing after miscarriage

Luciana
Hi everyone 
I just wanted to check with you if anybody had an experience similar to mine... 
I am 40 years old and just had a miscarriage in March. 
After that my first cycle came regularly after one month, and then strangely disappeared afterwards...just some spotting randomly...
Now 2 months without cycle, and not pregnant...did two tests and both came out negative.
I am freaking out...my doctor says to wait but she seems lost too.
Just wondering if anyone had similar experiences!
Thank you  xx
Luciana