Massive Ping Spike Help!

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I've had cable internet since 2005, and I don't believe my family has ever upgraded since then. My download speed (according to speedtest.net) is 3.36 mbps, and my upload speed is 0.84 mbps when not under a heavy load. I also did a pingtest, and that came out at 34ms. That being said, I never noticed any real issues while gaming up until a couple months ago, when I noticed the ping in all of my games would sky rocket (300's 400's 500's 600's 700's 800's even 900's). The router we're currently using is old and probably very dated, so I replaced it with a Linksys E1200 (NOTE: The other router is a Linksys WRT54G ver.6, and the modem is a Linksys BEFCMU10 ver.4. Also, the router would also occasionally crash as well, requiring a restart) router to the same modem. The pink spiking issue appeared to have been fixed, but then that router started to briefly crash every few minutes or so for a second or two. After that, I just ended up switching out routers again, so it's back to square one. Is there something going on with my ISP, do I need to change out routers and/or modems, should I change my internet plan, or what? NOTE: My ISP is Comcast