Am I allowed not to fast if I slept in and didn't make niyyah (itention)?

I was tired yesterday, and I couldn't help I just slept before even the sunset. Next thing I know I woke after like an hour after fajr time, I had slept for nearly 12 hours. Now I haven't taken suhoor I haven't even made my niyyah, and I feel so dizzy because I haven't eaten for more than 15 hours and now I have to fast for maybe another 15 hours. And I don't know if I'm allowed to not fast today, and then fast it back after Ramadan, because I didn't do my niyyah.