Can anybody give me some advice on wat to do about a lying partner?

my partner has been away since tuesday looking at a house to buy and working anyway he told me he was going to bed early last night and sleeping in his truck then he said he.ll b home in the morning. i rang him this morning bcause he normally rings at 7.30am to see if his son is ok i,m not the mother and his son is 7 anyway i rang him at 9am to c if he was on his way home and he sounded anxious so i had a gut feeling something was wrong so i asked him where he had slept last night and he started mumbling so i said did u go out and he said iwent to a pub with a mate for a few drinks and then i got some takeaways and went and slept in the truck, i had a gut feeling he was lying so i said no u werent with your mate and i made out that i knew this for a fact, i was bluffing,i asked him again where he slept and he carried on with his lye so i left it for an hour and then told him i acsn deal with the truth even if its another woman maybe you slept on her couch but i cant deal with dishonesty ican get on with it if its true n deal with it but u cant get on with anything when u don,t no wat your deaing with so he told me he rang an old girlfriend that hes known for23yrs and took her out to the pub and went back to her house and slept on her lounge he only told me this after i told him that he,d been seen and i toold him that you brought her a red rose as well knowing it was the night before valentines i was bliffing he went quiet now wat do i do, does anyone believe he didn,t sleep with this woman, he hasn,t done this bfore but there is always a first and he,s lied to the death of it only i made out he was seen and he fell for it wat should i do, it,s so unfair i,m stuck way out in the country looking after his son while he,s out on the town and probably having with another wiman and yes i love him he,s my soul mate or so i thought please help with some ideas