There are no therapists on here, we're just anxiety sufferers. You are suffering from obsessive thoughts, which all anxiety sufferers suffer from. So do all depressed people. If we didn't obsess over negative things we wouldn't have the problem. In your case, though, what you're obsessing about is justifiably raising concerns for you for more reasons than just anxiety. You must get into therapy and right away. If you can't afford it, and I mean truly can't afford it, there are programs for that. If you have insurance as you indicate, there are therapists who take it, just not the one you tried. On the website of your insurance company will be a list of all the providers who take your insurance, and then you call each one to make sure they still participate and are taking new patients. But one way or the other you must get into therapy as soon as you can, both to calm you if this is just obsessive thinking and in case your fears might have some validity to them, given you have said here you were aroused by pictures of naked children. What turns humans on can be pretty odd and doesn't necessarily have anything to do with what you're going to actually do, as you've found out -- you haven't done anything. But let's be sure, okay?
Pedophilia, or paedophilia, is a psychiatric disorder in which an adult or older adolescent experiences a primary or exclusive sexual attraction to prepubescent children (wikipedia). The fact that your primary sexual interests are not children (nor are they your only sexual interest) already means that you are not a pedophile. Don't worry about that term. On the other hand, you have had sexual thoughts about children and if that continues it should be addressed by a professional. I am not a professional in any aspect. Most people will call a person a pedophile if they are attracted to anyone under the legal age (usually 18 years old). That is not what pedophilia is. Someone under the age of 18 is a minor, not a child. Teenagers are usually adolescents, but age doesn't define "child", "adolescent" or "adult" when speaking scientifically. Legally a person is an adult once they hit the legal age in their area (again, usually 18). However, this doesn't mean that they are a child legally until they are 18. The legal term, again, is minor. A minor is not a child. People confuse this all the time.
A child is someone who has not yet entered puberty. For instance, if the person is female, they would not have started to develop breasts. They would be totally flat chested. Once a person BEGINS puberty, they are an adolescent. Once puberty has completed, that is when a person is an adult. None of this is defined by ages. Pedophilia isn't a legal term and no laws define it. If you find yourself attracted to people who have just started puberty and have some beginning characteristics of puberty, that is called hebephilia (usually aged 11-14). If you find yourself attracted to people in the later stages of puberty, that is called ephebophilia (usually ages 15-18). Most people have never heard of this so everyone just incorrectly throws around the term pedophile.
Now, all that being said, you need help if you continue to have any sexual thoughts toward children. In reading your statement (please try to use periods, it is very difficult to read/comprehend otherwise) it is a little hard to determine what is really going on as you seem to contradict yourself a bit. If you truly have never had any more sexual thoughts about children and it only occurred once or twice when you were younger, then I see no reason for you to be so concerned. Since you are clearly very upset and concerned I have to wonder if you don't have ongoing thoughts. Even if you are, I would be careful. Once you admit this to someone you could possibly have the local police notified about you. It could cause you many issues down the road. When police suspect you are a pedophile, guess what, they might not treat you very kindly.
If you EVER find yourself wanting to do sexual acts with children, have thoughts about abducting or grooming or otherwise interacting with a child in real life in any kind of sexual way, then yes, you should get help immediately. If you do not have these kinds of desires or thoughts, then I would stop thinking about it and move on with your life. No need to dwell on something that isn't happening anymore. But please, please get help if you are thinking about doing something in real life to/with a child.