What breaks the fast?
Short answer: Eating, drinking, intercourse, deliberate vomiting, menstruation, and nutritional injections or drips. Forgetful eating does not break it.
The fast is broken by: eating and drinking deliberately, sexual intercourse (which also requires expiation), deliberately vomiting, the start of menstruation or post-natal bleeding, and nutritional injections or IV drips. Whoever eats or drinks forgetfully should complete the fast: “Allah fed him and gave him drink” (al-Bukhari 1933). Brushing teeth, using siwak, non-nutritional injections and swallowing saliva do not break the fast. Read more: what breaks your fast.
Answered according to the Quran and authentic Sunnah as explained by the scholars of Ahl al-Sunnah wal-Jama‘ah. For your own situation, ask a trusted scholar.