Birth control can be useful.

Condoms will run out, eventually. And, unless you’re willing to embrace celibacy, family planning is best done in advance of disaster striking.

What are some other options?
IUDs – The intra-uterine device seems simple… install, ignore, repeat.. but they have been known to cause serious health issues and, without appropriate medical attention, these could become lethal.

Cervical Caps and Diaphragms – Block the little wigglers en route to glory. These aren’t fool proof, but they’re probably better than nothing. Ideally, they’re supplemented with a spermicide. Once you run out, are there any natural, safe options?

According to this study, lemon juice is an excellent spermicide, with pineapple juice coming in second, although likely intended for (ugh) post-coital douching: Spermicidal effects of lemon juice and juices from other natural products

The rhythm method – Using a calendar to determine when to get your groove on is not the most effective method of contraception. Having said that, it does put control into your hands, without worrying about finding or purchasing condoms or other items. For this to work, it’s crucial that you have a stable cycle that you can track religiously.

Cervical mucus method – During the course of your cycle, vaginal mucous changes in texture and abundance, signalling when you’re most likely to conceive. A clear, abundant mucous similar to raw egg white is an indication of ovulation.

Basal body temperature method – This very hands-on method involves having an in-depth knowledge of your body temperature during the course of your monthly cycle and tracking it religiously. It’s useful if your cycle is inconsistent. To use this method, record your body temperature at the same time every day (ideally in the morning) and chart it. The changes are minute, but over time you’ll be able to recognize the patterns.

For general info on natural birth contol:
https://www.celestialhealing.net/SexualHealth/natural_birth_control.htm

A medical person in official medical garb discusses the rhythm method: