How do companies determine your premium?
Some online companies return all quotes as preferred or tobacco use and do not take in account any height weight issues, or medical conditions. They correct your premium, issue exclusion riders or decline coverage only after you have submitted your application. The thinking is you have already invested time in the product and will accept the terms of the plan.

Give us accurate information and let us shop the market and show you only the plans that best meet your needs. We will prescreen your conditions and show you accurate quotes before you decide which coverage to purchase.

Premium is determined many factors and each company has its own policy for determining premium.
City, County or Zip Code
Age
Gender
Tobacco use
Height /Weight
Medical Conditions and Medications.

I think I have a pre existing condition. How will this be handled and will I be able to obtain health insurance? 
This is not something that is easily answered.
Some conditions are unacceptable by all companies and you will be unable to purchase a traditional individual health plan. ( Don’t Assume, Ask an expert with access to may plans.)
Some companies will rate-up (increase your premium) and cover your condition and medications.
Some companies will issue policies with exclusion riders (not cover) pre existing conditions.
Some companies will either rate up or issue exclusion riders depending on the condition and medications.
You need to talk to a reputable health insurance agent or broker that will help you find the company that has the best solution for your condition)

Companies that rate up for conditions may decline you for coverage if the condition is unacceptable. A reputable agent may be able to find a plan that will cover you with an exclusion rider on the condition.

Just because you have been declined by one company does not mean you will be declined by all companies.