Relationship advice?

​I lost my v-card to him and he lost his to me, but when he slept with this other woman it hit my like a brick because he is all I know. Well he magorly regretted it and spent a time period proving to me that I was the only woman he will ever love and adore. And after many months I took him back and I haven't regretted my decision ever. He is the only man I will ever be in love with and I'm sure of it. With some people you just know, but my question is.. Is it okay to still be sad and grieve over him sleeping with that other woman? I forgave him but I still am sad that I'm not the only one.