Help about finding out if my Bf is cheating

We have been since October 2015.
I had previously been thru a very fucked up brewk up(long story) but he basically cheated on my and fucked me over bad, taking 2 years to officially find my sanity. That's when I met my current bf.
After about 6 months-in April 2016, He was acting strange, volatile, snappy, secretive....I tried putting it aside and ignore it however that was impossible as that is what I did before, so this time I was not going to do that. He had always had his iPhone password lock on so one night I asked him what the passcode was, very very reluctingtly he finally let me know(after about a million why do you need it Questions...), so yeah he finally fell to sleep...I started digging... first in the line up of things found, was an image of a selfie of a chick in a bra with "LIZ" under it.
I went numb, started shaking, I literally dropped to the flood and sobbed silently myself-at that point I said to myself not to jump to conclusion, I couldn't listen when my gut instinct was dragging me to go. I asked him about it of course, his excuse was a spam email that he received....bullshit. I put it to the back of my mind.

Now we fast forward about 6 months later TO OCTOBER 2016-APRIL 2017
I found another email of the same liz chick but in a black corseette,written under the pic again was a word "MISTRESS". I lost my ****, but that wasn't to compare to the new box of condoms I found in his work bag about 3 weeks later. We were officially moving in together In a week and I find condoms in his bag-we don't use them as we're trying to concieve a baby. So I lay in the foetal position and wept, his excuse first was they must be old ones from his previous girlfriend, then when I showed how they have a time stamp of expiration date which you can estimate when this particular stock was made and shelved-he changed it to he had used them as a practical joke at work to fill them with shaving cream and leave them on A work mates seat. I had nothing of it...today I still have nothing. And the last one was in April when I came across an actual email from him to some sex escort worker, I remember only parts of it-i was in shock after all. He swears to me that he never followed up on it, but frankly I'm not convinced one bit. And now I'm suspicious of finding a popped out PRE PAID SIM card with an expiry of 2018 and he said he changed his number after I found random mobile numbers throughout his phone and call contacts. What I'm mostly suspicious of, is that he says his previous number ending in 467 he has had Vodafone change to another 822, known as porting. However, I'm Not convinced one bit that he completely retried the number-in fact I'm pretty sure he just transferred it over to another provider, like Optus.

Long story short-I AM NEED OF ANY HELP OR ADVICE REGARDING FINDING OUT AND PUTTING MY SUSPICIONS TO REST. ANYBODY OUT THERE WHO CAN ADVISE ME WOULD BE GREAT. XXX