my citizenship status

i was born in UK in 1985 . me and my family obtained an ILR after i was born by two weeks . then we left UK but kept our ILR for many years im not sure how many . then we lost it as we couldn't travel to UK. I live in sudan . I'm a well off dentist . i have a british sister who is a certified doctor in UK. what is my british citizen ship status now ? can i apply for it? am I eligible?

Have a look at this UKBA webpage and in particular the sections headed "If you were born in the United Kingdom on or after 1 January 1983" and "If you were born in the United Kingdom to parents who are not British citizens and are not legally settled here".

You tell us "me and my family obtained an ILR after i was born by two weeks", so was in the case that neither of your parents had ILR at the moment of your birth? Or did either or both of them have ILR when you were born, and then merely got your ILR about 2 weeks after you were born?

Dear sir ,

I'm well informed about the fact that I'm not automatically a British citizen because my parents gained their ILR after my birth. Maybe i should have been more specific . Do i fall under section 3 of British nationality act of 1981 or is it just for minors or if my parents still have the ILR until though they gained it and lost it before I turn 18 ? I meant can I be registered as a British citizen in my adult life with a proof that my parents had the ILR before I turn 18? Thank you for your lenience .

Best regards,
Dr. Abdalla

Section 3 and Section 1(3) are for minors only. If UK-born people have lived their first ten years continuously in the UK, then they are entitled to register under Section 1(4).

However, applicants age 10 or over are subject to the Good character requirement (including not overstaying, when 18 or over, etc) (41A).

Good character and applications for citizenship > Hiri v Secretary of State for the Home Department [2014] EWHC 254 (Admin)
Hundreds of children refused British citizenship on character grounds > Applications by minors for registration as British Citizens
Refusal of a child’s British citizenship application on character grounds overturned > SA, R (on the application of SA) v Secretary of State for the Home Department [2015] EWHC 1611 (Admin)
Supreme Court finds British nationality law discriminatory, allows appeal on human rights grounds > R (on the application of Johnson) v Secretary of State for the Home Department [2016] UKSC 56.

(35-50)

See also Response to an inspection of the Home Office’s application of the good character requirement in the case of young persons.

So s.abdalla, as a question of fact, did you spend the first 10 years of your life in the UK?