#4 is definitely a red flag.
Cheating is probably the worst thing that can happen to your relationship, and it has ended many amazing relationships, but carrying it even after knowing the truth is not a good thing either. What could be worse than cheating? Probably nothing. But there are other habits as well that can turn out to be way worse that bringing in a third person in the relationship.
Here are some things that definitely prove to be more horrible than cheating over a period of years.
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They could be harmless lies, but they still matter in the long run. For example, he told you that he's working late but he actually went to a friend's place to watch the match. They could be nothing at first, but things like these build up over time.
Communication is the key to any relationship, but what if your partner has a habit of holding a grudge?
Encourage your partner to drop the silent treatment and talk about matters right when they arise. Talking about problems can really help.
Every relationship tends to get comfortable over time and people stop putting in efforts. If he's not as invested in the relationship or doesn't try to resolve matters because he knows you'd do it eventually, then there's a problem.
Eventually, the relationship is going to get exhausting at your end because he will withdraw from all responsibilities sooner or later. Either walk out now or make attempts to get his act together.
A little bit of jealousy and possessiveness is natural in a relationship. Feeling jealous when you see your partner with someone of the opposite could be a very natural reaction, but only when it is confined to limits.
Talk it out with your partner instead of letting the tension build up. It will explode in your face sooner or later and it could prove to be fatal for the relationship.
People put up a guard around themselves so that other people don't see their real side. Although, it is alright to adjust according to the people you're around, but it is not fine to fake it with your partner.
Nobody can hold up the fake act for a long time. If this is not what you want in your relationship, ask your partner to change or walk out.