Is your significant other being shady? Do you have a gut feeling that he/she is cheating on you? If so, I would listen to that gut feeling if I were you. We, as women, have been blessed with having great instincts. I have found that 99% of the time, that "gut feeling" is right. Don't ignore it like I did.
Pay attention to red flags. Does anything seem off? Is your partner acting weird or different? Don't write these things off. I know that it is so hard to face the facts sometimes, but you really need to protect yourself in times like this.
Once you two are officially broken up. Do not keep texting him/her. Do not keep hanging around him/her. Just leave him/her be. It will save you so much hurt and so much time. I know it is hard, especially when they are the one to initiate the conversation, but just cut them out. If they are willing to cheat on you, they do not deserve your attention. Do not let them convince you that there is hope for you two to get back together. Even if there is, they will probably hurt you again.
If you truly think they are cheating, talk to them about it. Give them a chance to tell you everything. Once you know that they are, break up. Don't go back.
DON'T stalk them on social media. DON'T stalk their new girl on social media. DON'T bash either of them; it will not make you feel any better. DON'T lay in bed and make yourself miserable. Just try your best to forget about them by picking up a new hobby and hanging out with your friends. Learn from my mistakes so you can live a happy, healthy life without them.
I promise you, it will get so much easier with time. Everybody involved will be so much happier if you just leave it be. You will move on. You will find someone that is so much better for you. You are better off without them.
