9 yr old ear ache, no infection found

[Fisharesexy]

Hi, my 9 yr old has had an ear ache for around 5 weeks. It started in both ears after a cold.
He has been swimming at school for 5 weeks, is this the cause maybe?
Doctor visit after 3 weeks, no infection, soreness etc but small amount of fluid behind each ear.
He has a history of ear infection, mainly when he was young. Very rarely gets fever and discharge from ears.
Ears hurt when change in weather.
Doctor says to monitor, she thought one ear canal was narrow. No hearing problems in school.
His dad and I have tinnitus, loud noise and thyroid issues. Minor, doesn't affect lives.
I think my family have eustachian tubes that struggle to drain, me included.
Worried about this, anyone help?
Thanks

I mean tinnitus caused by husband being in band and my thyroid issues. Thanks

Often after colds children can have problems with residual fluid/glue build up behind the drum, causing pressure problems in the Eustachian tube, which can cause pain sometimes as it resolves. Our daughter has a health condition which means she produces excess sticky mucus all the time, and often has ear ache without infection, hurts in her ears when she swallows etc... Hopefully it will pass soon.

Thanks, I used the coarse sea salt in a white sock trick. Heated in a pan. Worked after 2 goes. Coincidence???? Anyway, just happy it's gone