2 steps forward, 3 back

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He says he will not come back, even if worst choice ever. Now has GF of 6 weeks who is over every night, eats with MY family and he took them all to the shore for the weekend and they slept in the same bed. This is killing me! I can't eat or sleep, lost 28 lbs so far, I am obsessing. I really need help but cannot seem to stop this. I want my marriage back so bad I would literally cut off a limb to get him back. That is pitiful I know but I hate being alone and lonely and jeleous and hurt. I am a wreck!!! Haven't been this bad since he left until GF showed up. He tells me to move on, its almost been a year. I said 9 months and he was still my H. He said he was not. I said legally he was. I cannot stop. Any advice other than get over it and focus on the kids. My head knows it all but the heart keeps blocking common sense. Help me please