Delayed Period?

I'm kinda freaking out cause my period is one day late which is very rare for me. I'm on birth control and I'm very regular. I was on antibotics the Z-pak which I finished 2 days ago. I was not ually active at all while on the antibotics and haven't been since I started taking it. I was really sick though, it's the sickest I've been in 3 years. I think I might have had bronchitis and I'm still not 100%. Could this have delayed my period? I took a home test and it came out negative. Am I feaking out for nothing?