I read but didn't respond to your earlier one. I am in a long term relationship and have no grounds to suspect my partner would ever be anything but faithful . However I was in a previous relationship were there was frequent infidelity - can not get past this and when feelings of paranoia have surfaced have taken to checking phone, letters etc. Its not him but me that has the problem.
Also trust him implicity with with my life, money , with the care of others, but not to load the dishwasher properly!