(First, "gonna" is not a word in standard English. It is the way some people pronounce "going to".)
It's a little wordy. If I had to choose one option it would definitely be "It was as if I was going to fall over." I think it is more typical to say "I felt as if (formal) / like (informal) I was going to fall" or "I thought I was going to fall." The "over" is unnecessary here.