Seventh-day Adventists are Christians! Technically speaking, all of Christianity is a cult in that we are devoted followers of Jesus Christ as our Lord and Savior.
Unfortunately, "cult" is a word that is often carelessly used, misused and/or used to defame someone with whom one disagrees.
The primary dictionary definition of "cult" actually applies to nearly all religions and/or faiths:
1: formal religious veneration: worship
2: a system of religious beliefs and ritual; also its body of adherents.
Most often only the 3rd (primarily), and 5th definitions are actually what is intended:
3: a religion regarded as unorthodox or spurious; also: its body of adherents
4: a system for the cure of disease based on dogma set forth by its promulgator (health cults)
5 a: great devotion to a person, idea, object, movement, or work.
All forms/systems of religions and religious faiths have certain "standards" or belief systems by which those who choose to associate with the group agree to and accept. (The same is basically true for many social organizations, such as clubs, political parties, philanthropic organizations, etc., etc.)
A number of Christian denominations and even other non-Christian religious faiths require or request one or more beliefs and/or standards in common with the Seventh-day Adventist church.
Because the Seventh-day Adventist church is a well-established, organized Protestant denomination, accordingly, it is inaccurate to refer to us as a "cult" in the negative way.
As for your personal struggle -- I believe that God does want us to enjoy life - but that He has laid a framework within which we can both be happy and be in harmony with His will for our lives!
I believe that every human being has at least one "fatal sin" (some of us struggle with more) - it is the one sin that we struggle with, and which is hardest for us to let go of. God, however, wants 100% of us. Whether you were a Seventh-day Adventists or not - only you can decide whether you want to follow God's plan for your life or not!
Finally, this is too important an issue to leave up to Yahoo! Answers!! It is a matter of eternal life and death.