OCD is sometimes called the 'doubting disease', as sufferers can feel plagued with doubts and uncertainties. There are different types of OCD (some common types are Checking OCD, Contamination OCD, Rumination OCD, Religious OCD), but the good news is that all types of OCD have common features and therapy can certainly help begin to tackle this problem.
OCD is often quite misunderstood and can be hard to spot - people who have never experienced the condition often associate it only with quite narrow behaviours of the kind featured in TV shows, such as extreme organisation or, say, a strict preference for routines. While these may indeed be OCD traits for some, it's also the case that there are many other presentations of OCD that are not an obvious fit for the best known cliches. It is worth talking to a therapist about this.
OCD sufferers will tend to have intrusive thoughts to which their OCD attaches a great personal significance. 'Having the thought in the first place' is often felt to be very significant too ("Why did I have this thought?! What does it say about me?!" etc). Having had the thought, an OCD sufferer will typically carry out compulsions - sometimes called rituals - to try to neutralise the sense of danger and anxiety the intrusive thought provokes. This becomes a closed-loop, where the strategy to reduce anxiety (the compulsions) actually begins to reinforce the sense of danger caused by the intrusive thoughts.
OCD can be a very debilitating condition for sufferers and I encourage you to get help to begin to beat it once and for all.