I'll talk like i would to my grandma because i don't know your nerdness level:

- Use cl_autotimenudge 1 ('negates' up to 20 ping ms)
- Close all background processes witch may consume bandwidth
- Stop downloading pr0n
- Disable steam updates while ingame (i think it's on by default)
- Make sure no other devices in your network are clogging up your bandwidth. You can test this by progressively shutting down every other device until the only one left is your pc. Make a ping test toward a game server for every device you shut down. Your router may also have a builtin utility for checking bandwith consumptions per connected device. Also make sure your neighbours are not "borrowing" your connection.
- Ask your ISP for a check

Also remember that 38 'default' ping you mentioned only means your router took 38 ms to communicate with the test server you used, which most likely is not the same as the game servers you're trying to connect to. Geographical distance will increase ping times...

When this happens to me, it's either windows 10 with its nazi update policies, or my friends using facebook from their smartphones.

ASD

Play on servers located closer to you.