English into Old Tongue translation

Hi, I posted this is a WoT Facebook group and someone suggested I try here, so here goes:

My wife and I are celebrating our 15th anniversary this year. As gifts we are giving each other rings inscribed with a message in the language of our favourite series. She is giving me a ring inscribed in Elvish from the Lord of the Rings, I want to give her a ring inscribed in the Old Tongue. I'd appreciate some help with the Syntax of my message.

The message is: "On our anniversary, you own my heart. Through the anxiety and pain, I will always be there."
 

The translation is: "Ost fel Shanna'har, macovale cuebiyan. Cuardein mirhage, hei zaviltye koja."

I used the official Tor English to Old Tongue dictionary, but the middle part has me stumped, I'm not sure if it's written correctly.

Any help would be appreciated. Thanks.