Can I downgrade still?

Hi. I have the iPhone 4s and iOS 8.0.2. My brother installed it last week on Thursday. iOS 8 has made my phone slow and glitchy. My phone calls cut out, my phone turns off randomly, I can't text anyone and my apps disappear randomly. I only have 3 apps now because I had to delete the rest because they would close randomly. I know that all the news sites are saying that apple has stopped signing iOS 7 but I need some way to downgrade. Is there a program or jailbreak to help? I am really tech savvy so I can figure it out. Please help!