I couldn't tell anyone for fear I wouldn't be able to compete in the Olympics if people learned I was HIV-positive.(Para.7)
Meaning: I couldn't tell anyone in case I wouldn't be able to take part in the
Olympics if people knew that I was infected with HIV.
for fear: for being afraid
"For fear" is often followed by a that clause.
He set off very early for fear that he might be late for the interview. 他早早就出发了，生怕面试迟到。
compete: vi. take part in (a game, match)
Our school competes against many other schools in baseball. 我们学校常同许多其他学校进行垒球比赛。
The boy was reluctant to compete for the first time in front of his parents. 那个男孩第一次当着父母的面比赛，心里有点儿紧张。