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Short answer: YES.
You NEVER reuse a condom. NEVER. Even if you wash it really thoroughly, you cannot use it again. (If, by chance, by "it" you mean his penis, washing the penis isn't a method of birth control either, and will not prevent pregnancy.) And if you take the step of having sex a second time minus the condom, then you are running a GIANT risk of getting pregnant and spreading infections.
To prevent pregnancy and STDs, you must use a NEW latex or polyurethane condom from start to finish for EACH act of intercourse -- the condom goes on when he gets hard, and stays on till he finishes and pulls out. If there is ANY contact between your genitals without that condom on, then you have not used it correctly, and you cannot rely on it to protect you fully.
We have some articles about safer sex and condom use. You really ought to read them: