2004 Honda Civic 2 door coupe. Two days ago, while driving, my radio turned off, then I started hearing a clicking noise that went away when I turned off my AC, and the car seemed like it was going to turn off occasionally, but didn't. Acceleration became weak for just brief and sporadic moments. I brought my car home and it wouldn't turn back on after turning it off. It made that machine gun sound cars make when battery dies. I figured it was the battery and I put a new one on there 2 days later. I should have tried turning it on just before installing the battery to compare, but I didn't and it turned on like normal after installing. Well, today I drove it for the first time and when returning from work it started doing the same thing it did the very first day (radio going in and out, AC making clicking noise, etc.) thankfully when I was close to home. Turned it off, and when I went to restart it I heard again the machine gun sound and the gas, speed, revs dials went haywire for a moment. Confession: it was about to rain when I went to install the new battery and never actually tightened the connections, just made sure they were on there. I just tightened them but even after doing so the car made the same battery-dead sound. Not sure what to try now and wondering if anyone had any suggestions. Please explain as if I knew very little about cars. Thank you very much in advance.