A guy in a womans world?

I'm just looking for some good advise on how can I convice my woman boss to concede me a monetary raise. See the thing is that I work in a place where all my bosses are women. We have a Director, she is the big boss, followed by 3 managers who are also bosses, there is about 6 group leaders who are also bosses. My co-workers are 90 % women and I really like working in this enviroment. I've been working in this pre-school program for 18 years now. The thing is that over the past years all this people have got very good raises and as for me I'm stuck in the same salary for the past 8 years. I've tried dialogue with my main boss, I've written letters and the last time I sat down with her she told me there was nothing she could do. My evaluations have been outstanding, my overall task and performance have also been outstanding, never had a warning or problems, I feel my relations with my peers are very well. The thing is that I do not understand why this atthitude towards me. Sometimes I believe she could be influenced by somebody else or she plainly she doesnt believe I deserve a raise, but she does not tell me. In the past weeks new workers were hired and all of them top me in salary even though they don't have the work experience. Like I said I do not have any thing against working in a womans enviroment but this situation has really got me confused. I just need some good advise. Women are very welcome to given advise on what should I do and as other persons who have experience similar situations. Thanks