please ladies need advice on this man of mine is this a beginning on him cheating

Ok girls need some advice 
My boyfriend works in a warehouse we been togeather 6 years and found out over Christmas we are exspecting I am so excited 
It's our first 
Let me just get to the point well he speaks to 2 girls at work that I don't mind as I serve 1000 of men a day at work 
But the only thing is he blocked both girls on Facebook I asked who they are he said he Dident know I said well sure your know as there in your blocked list on Facebook in the end he said he Dident want anyone to come between us so he blocked them 
Why would they even wanna inbox him to start off with if there all just friends at work 
He lied to me first and so many questions are going through my head why else would he of blocked them 
The 2 girls are actually sister he left me 4 years ago for another women and I met someone else we then got back togeather a month after I'm scared that he's going to leave me for someone else I haven't got the perfect body and I am not pritty so I feel like I am threatend by this am I being paranoid 
Please lady's give me some advice on why maybe he's blocked them lied to me first and then told me they work at his place and all he done is speak to them why would he block them if he want nervousness of them coming between us why would they in the first place 
If you have any idear on why 
I am just scared of him leaving me 
He said he loves me but then he said he would have a better life with them 
But he's happy with what he has here 
What should I do