HER NEREDE OLURSAN OL HER ZAMAN YANIMDA OLDUĞUN VE HİSSETTİRDİĞİN İÇİN AYRICA TEŞEKKÜR EDERİM.DOĞUM GÜNÜMDE YİNE BENİMLEYDİN İYİKİ VARSIN SENİ SEVİYORUM....

my "free" translation:

no matter what, you were always there for me and........I thank you too. I´m glad/happy you were with me on my birthday.I love you.

iyiki varsın,,,I´m glad/happy/lucky you are/exsist,,,,,don´t know if I got this right,maybe it is better: i´m happy I have you??

hissettirdiğin için,,,,to make me feel??

thank you

From my point of view, there are problems in the Turkish statement. I would write it like this:

HER NEREDE OLURSAN OL, HER ZAMAN YANIMDA OLDUĞUNU (BANA) VE HİSSETTİRDİĞİN İÇİN SANA AYRICA TEŞEKKÜR EDERİM. DOĞUM GÜNÜMDE YİNE BENİMLEYDİN. İYİKİ VARSIN! SENİ SEVİYORUM....

Or a second version would be like this:

HER NEREDE OLURSAN OL HER ZAMAN YANIMDA OLDUĞUN VE BUNU BANA HİSSETTİRDİĞİN İÇİN SANA AYRICA TEŞEKKÜR EDERİM. DOĞUM GÜNÜMDE YİNE BENİMLEYDİN. İYİKİ VARSIN! SENİ SEVİYORUM....

The translation is :

No matter where you are, I thank you alot that you always give me the feeling that you are with me.  You were again with me on my birthday. i am happy that you exist! I love you...

I hope this helps.

thank you very much!

I have one more question; does this "iyiki varsın" always mean present tense(now)? how could I say this in past tense? somehow "vardın" doesn´t sound good in my ears

It is an idiom. Dont change it.