Iam having doubt that my close friend & my wife cheating with me

Two years back I got in touch with person who is working with reputed company,slowly we are became very close friend coz he had been helping me financially when I was under financial crises.I was very impressed @ his friendly & co-operative nature & become familiar soon. But after year later My family got preganent. My wife & me are very happy @ our decision of third kids.Days were passed away happilly & God blesses a very quet son. But surprizingly my friend also excited very much like me. I am ignoring my self /my thought but day by day my friends attachment toward my third kids increased aggressively, he was feeling hurted in small-small space between him & my newly born kid.I had been surprize & became apsets on my wife . Many times we had a fight between us .There are continuous discussion started between my wife & friend ,Many times I taken objection on my wife by intrupting their phone calls but each time she shown & react aggressively that she was nothing doing any thing wrong & reply that she is talking with his sisters.
On first birthday of my son my friend made big karizma album of my childs photos; all are clik by him & wife,Actually I refuses him initially but then later he forces me to accept. But I seen that he purchase big scotter toy for my kid. Then I got very very upset on my friend & stopped talking with him.parallaly fightted with my wife also.My major helplessness for couldn't taking any action on my friend is that He had supports me & my family in my very crucial priod also he help lot to start my own business.
There is one major weakness is that I am having three kids & all are below 10 years in age.My wife is not accepting any thing.
My current difficulties are
- I don't have clear evidence of affairs
-Affair is with my very close friends who had help in my crucial period
-My kids are small so any crise affects on them also

my doubts are not clear yet .still I got feeling that both are cheating behind me.what should I do

redg
BMR