All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
As you know that engagement or promise of marriage does not justify having relations with a marriageable man. The details are mentioned in our Fataawa: 81668 and 81356.
What you did is a sin, so you have to sincerely repent from those sins. To know how to make repentance refer to our Fataawa: 81467 and 88178.
No doubt, that sins and disobedience of Allaah, the Glorified and the Exalted, cause Allaah's Wrath and displeasure. So, one should try to do good deeds as much as possible as an expiation for his/her sins. The Prophet instructed us, saying: "Fear Allaah wherever you are; following an evil deed with a good one obliterates the evil deed; and deal with people with good manners." [At-Tirmithi]
However, do not be sad for some hardship that befalls you, as everyone in this life suffers. Yet, a believer should always be patient and thankful to Allaah, the Glorified and the Exalted, for His great and numerous blessings.
Allaah, the Glorified and the Exalted, knows best.