How to come out of the negative thoughts

I am in a relationship for about 2 years and we stay very happy with each other 95% of the time. Now our families want us to get "married" and both of us dont beleive in this institution. But he is ok to do it so that people will not disturb us with this. I am not ok with this since i will be faking it. Moreover, it is creating a weird feeling in my body like palpitation. I dont think it is fear, but i dont know what it is. The more I am being pushed to do it the more this palpitations increases. I had a bad marriage experience earlier, so everybody thinks its a repercussion of that experience. My symptoms today are: Intense negative feelings. I feel I am being forced. Self harming thoughts. Feeling i dont fit here. I had an emotional breakdown last night, followed by a big fight with my boyfriend. I lost control of my mind. There was also a stammering for a few seconds, which i never experienced before. And coninuous crying. Now I am not able to my brain from thinking negative thots.