I don't know what do. Help please

So I'm in a relationship with this amazing person and I truly enjoy them being with me, however I keep getting jealous because they flirt with other girls and tell me that it's just a joke and that I'm the only girl they love. I believe them but it's sometimes hard to not get jealous when I literally see them flirting with my friends..... Anyway, they recently messaged me about going on break for 3 days to show their friend that we're truly in love... I feel like I'm making the wrong choice and giving them 3 days to actually be with someone else instead of me or doing things that aren't right. Am I overthinking things or should I just relax and wait the 3 days?