My battery icon shows the lighting bolt but isn't charging

Yeah, I did the different ports earlier, with other chargers and in different positions and everything. Just tried what you suggested- the diagnostic didn't find anything and resetting the NVRAM/PRAM didn't seem to have much of an effect. I'm beginning to think that maybe I'm cursed.

I would not hesitate to take it in to the store—In or out of warranty you can get a free over the counter 'Apple Service Diagnostics' test. Go from there, seems you have covered all the bases.

make an appointment

https://www.apple.com/retail/geniusbar/

https://checkcoverage.apple.com/

https://support.apple.com/my-support

https://support.apple.com/en-lamr/aasp-program

May be easiest to make an reservation from iOS online Genius Bar appointment app: 

https://itunes.apple.com/us/app/apple-support/id1130498044?mt=8

<< I thought I had fixed this issue last night after resetting the SMC and

switching to the lower port, and sometimes it seems like its working

again! >>

Resetting SMC is the go to way to reset the battery management/charging. If it seems to be working now, ?

You do not say what exact Mac / model / year /size /retina /touchbar ?

Barrel-type connector, "T" style MagSafe connector, "L" style MagSafe connectors, MagSafe 2 connector, USB C ?

The magsafe connection on the DC-inboard can get worn. Reversing how you plug it in, twist slight to regain contact all can help.

You can read through Apple Portables: Troubleshooting MagSafe adapters - Apple Support

Have you tried different ports—same result?

Charging and Expansion

Two Thunderbolt 3 (USB-C) ports with support for:

• Charging
• DisplayPort
• Thunderbolt (up to 40 Gbps)
• USB 3.1 Gen 2 (up to 10 Gbps)

Rebooting/restarting defines port definition,

manually this is done by resetting NVRAM/PRAM http://support.apple.com/kb/ht1379

This would be worth a try. If no resolve ...

You can try running the Diagnostic/AHT  http://support.apple.com/kb/HT1509