You can't reuse a condom as they're only designed for a single use. Although the condom may look perfectly fine after use, they're often prone to splitting, and the holes are very difficult to see with the naked eye.
Other contraceptive methods
If you're worried about the effectiveness of condoms, there are other contraceptive methods available, including injections, implants, intrauterine device, pills, and many more.
Ultimately, you should never try to reuse a condom. There is a high risk that it will not be suitable for use, and it's not fair to your partner, yourself, or the child that's potentially born from a lack of proper protection.