我的建议：
在felt前面加suddenly（突然地）,整个句子改为I suddenly felt dizzy when I was riding and fell down from the bike.
下一句,woke 后加 up.然后在hospital前加the.（注：in hospital表生病住院；in the hospital 在医院里.此刻由于“我”刚醒来,所以觉得用in the hospital好一点).
下一句：把 told 改为said.told多用于间接引语,而直接引语常用said.
最后一句：句首加上he said ,并把will改为would.
嗯 都是些小问题 .
That's all.