@sarah8484, sorry again for derailing your thread.
Yes, you'll be sad. Then you'll find something that will be like a massive punch to your stomach, and this will disorientate you. It will be when you start questioning yourself. When this happens, behave as normally as you can and don't do the 'pick me dance'. Play it cool.
Here is my suggestion:
The next time he nips out to give a quote or meet his uncle/mate Steve/colleague Dave or whatever, phone him on some pretext. If he answers, he will probably sound weird or ask if he can call you back in 5 or 10 minutes. If he doesn't answer, it will be because his phone is switched off or in aircraft mode or on silent.
If he's nipping to the shop or something ask him to pick something up while he's there. Pint of milk or bar of chocolate or something. If his mind is elsewhere, he'll forget, or he'll make a big deal that he got it for you. Probably.
Signs to look out for include sex. Do you ever get the impression that he's not really enjoying it with you? Or has it improved noticeably?
Has he changed in the way he speaks to you? Become more critical or anything?
Have you started to feel excluded?
Has he started making more of an effort with his appearance?
When you have proof that something is going on, 'get your ducks in a row'. It sounds like a cliche but get your plan together, know where you stand legally and financially.
If you have children, watch for him minimising his income to give you less child maintenance.
I hope that there is nothing going on, but your gut is telling you for a reason.