It is completely normal to have anxiety and doubt yourself when you are learning something new and / or starting out at a new job. Even more so when companies do not provide adequate training for the job, or (as Mathew Gaiser pointed out in his answer) proper instructions.
When you ask whether you are a right fit for the job, you are essentially trying to evaluate two things:
- Do I have the necessary skill-sets to execute the tasks assigned to me?
- Do I enjoy executing these tasks?
In your case, you are perhaps doubting yourself based on the first and wondering if you lack the qualifications or skills required, and whether you can acquire and become proficient in them. Moreover, you feel the added stress of seeking help from colleagues.
If you have received proper training and mentoring, and still feel you aren't proficient at executing your tasks after 6 months to 2 years, then perhaps the job isn't right for you. (I say 6 months to 2 years because not all jobs are the same and some jobs really do require more hands-on experience before you can be good at it - speak with experienced people in your industry to determine how much time it takes to be adequately proficient in your field).
Till then, you can focus on the second part - find out if you enjoy the job and if the future opportunities ahead in your field excite you? (Note also that your employer hired you because they saw potential in you and were satisfied with your qualification).
As for seeking help from colleagues, don't stress about it. It is normal for any colleagueanyone to sometime feel a bit irked by the demand you may place on them when you ask for their help. Especially if it means they have to divert attention from their tasks. It is unproductive to over analyse their words or actions. Instead, if really necessary, learn to seek direct clarification non-confrontationally.
(Don't let a real or perceived bad experience stop you from asking for help though. If they can't or don't want to help they will tell you so and it doesn't really have to mean anything more - you have the right to ask someone for help and they have the right to say no, for whatever reason.)
Meanwhile, be grateful to those who offer their valuable time to you, and, more importantly, show your appreciation to them by doing something for them too (e.g. by helping them out with their tasks at work or buying them coffee or a meal or even giving them a gift for some occasion).