Other than hire specialized security services there is only so much you can do to eliminate reasonable doubt.
If the camera isn’t connected (wired or wireless) then he needs access to get the data. Does he have access to the house? Does he still have a key? Changing locks is dead easy and generally only requires 15 minutes of research on Youtube and a Philips screwdriver. Even if he’s registered to the home, you can change locks on the pretext you lost a marked keyring and that he can contact you if he needs access.
The camera might be connected to the phone-network, but then he needs to power it. Search each and every outlet and see what’s connected. On the off-chance he’s direct-connected it to power then look for cables running from lights to some unexplained area. I however doubt he would spend the money and do the work to go that far. A battery operated camera would require recharging every couple of days.
Unless he has an unlimited budget this could be 1-2 cameras. Look in the most likely areas. He won’t spend money installing a camera or bugging device in the garage or kitchen, but more likely in the living room and possibly bedroom.
Do you have a security system? Is it accessible offline or outside the home? Like can he log in? If so look up how to change passwords.
As mentioned you can get $$$ devices that do a good and detailed job, but you can also get free software that does a good-enough job. You can even probably log on to your router and see what’s attached. If you don’t have the technical ability and the router is provided by the ISP their hotline can help. Might even be enough to reset the password (my suggestion: mySoontobeexHusbandhasa1inchmicrodick)
Look at your router. Any ethernet cables you don’t know the function of? A quick and easy way to discover the function is simply to disconnect. Disconnect cable A and the Internet disappears = that’s the one that connects the router to the provider. Disconnect cable B and the TV signal goes = that’s the one that provides TV. Disconnect cable C and nothing happens… might be a camera. Leave it disconnected.
Comparable advice for bugging equipment. Even the best needs to be connected to power or replaced regularly to recharge. Do you really think he’s snooping around your vehicle with the spare-keys every second day to switch bugging equipment?
It’s highly unlikely that he’s bugged or is tracking the vehicle. Unlike movies where the suave spy simply clips a coin-size disk under the fender it’s a lot more work. For one you need access to power, so when fleet-cars have monitoring installed it requires rewiring. Do a detailed but reasonable search of your vehicle. Don’t forget to search in the pockets behind the driver and passenger seats.
We have had comparable issues here on this forum. In that case it turns out the husband still had access to phone-records online as well as location tracking on an old computer. Go change all your passwords and turn off location services. Maybe even a factory reset on your mobile.
What about old computers, phones and pads? Any chance he still has one?
Change PW on all accounts, networks, devices…
"If, therefore, any be unhappy, let him remember that he is unhappy by reason of himself alone." Epictetus