www.ocfoundation.org is a good site for info.
i think the general professional opinion at this point is that Pure O isn't really anything different from regular OCD. when people say "purely obsessional" that is almost always inaccurate. they have compulsions just like anyone else with ocd, only the compulsions they engage in are mental rather than physical, and aren't something that can be observed from the outside, or are primarily avoidance compulsions (for instance, people who are afraid they might be gay often will avoid looking at anyone's body who is of the same sex as them, and would only look at their face, or avoid reading articles about gay pride, along with constantly reassuring themselves that they aren't gay, or engaging in a compulsion of trying to analyze and figure out whether or not htey are gay or quantifying their feelings, and what evidence they have for and against it. or they will dress certain ways and talk certain ways to be sure that they aren't appearing gay to others)
even in your description of your new fear, you've already mentioned a compulsion, "checking"... additionally, you avoided saying what your fear was, presumably because you are scared to say it because you feel it is so horrible and unacceptable, and fear how having that fear would reflect on you... which is also a compulsion.
people who think their ocd is purely obsessional tend to have a harder time with getting effective treatment because they think ERP (exposure and ritual prevention) won't work for them because they don't have rituals/compulsions. in reality, ERP is still the best and most effective treatment, you just have to get more creative with thinking of how to avoid rituals or purposely do things that set of the anxiety