am I overreacting or thinking to much

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So I'm going to try and make this short as possible... three or four weeks ago I broke up with my girlfriend because her ex called her and brung up memories and she told me she still in love with her so start thing to do is to break up with her I know I should've just moved on but I had feelings for her.. anyway she then told me her ex said she didn't love her etc so she eased her way back to me and told me that she didn't love her ex because you know when you love someone or in love with someone so I took her back it's been two weeks since this happened And like an idiot and i forgave her and make jokes about it once in the blue now I got an opinion from an older person when it first happened and I saw the person today and he basically brung up all of these feelings and he's like oh she seems confused and only wanted you because that didn't work out now the guy is older and married so it's not like he wants me but he's not the only person who said this now I'm just thinking about it all Am i over reacting because i told her I forgive her or should I feel this way idk I need advice someone's opinion   
Sn: when we were not together she would play the part she would text her ex good morning beautiful and be cute but text me hay or hi and says oh because you were being mean but now that we are back together she text me cute stuff everyday