I think my boyfriends havd been cheating on me

Jade
I don't want to get into details but the other day this number called my phone and I picked up and they said they have the wrong number , and it sounded just like his ex. I want to know who she is & why would she accidentally dial my number. Maybe I'm being crazy but she sounded just like his ex that I'm assuming he has been talking to & I want to find out but don't know how. I called back private and she said hello and it sound just like her. What should I do? Please do not say just ask because honestly let's be real he is not going to be honest with me or her. I texted the phone from another number yesterday and acted as if I was someone looking for "David" which is my bf and they never replied.I think she know its me because she knows about me