For a while i suspected my husband is havin affair with my best friend,?

for a couple months i suspected my husband and best friend were havin affair, we have a stud farm and she comes and stays every weekend to help with horses so i can have time with my hubby nd kids. it started when i thought he was in the bathroom while she was bathing one early morning but i said nothing as i convinced myself i was dreaming. she will sit on his knee while i sit on the floor if we have guests over then my dad got took into hospital, and devastating news came on the friday secondary cancer with no primary my life just stood still in time how do i manage without me dad. the next day i had a bday party for our daughter and again she sat on his knee very cosey so i hit the bottle my head blew, they sat up till early hours, my cousin slept on chairs in the lounge next to the couch, were them two were and on tuesday she said my hubby made a pass at her he says he cant remember and doesn't want her up farm again but she wants to come up i sit and talk to docs and all i can think about is them two i walk round farm and see them together i am going crazy demented