Thanks for writing in to us at AlterHéros. From the sounds of your post, it seems that you have become increasingly depressed over the years regarding your strong feelings towards potentially being a woman inside. You also mention that if you were able to pass as one, you would worry that you wouldn't get the support that you need from your family in making the transition.
When it comes to figuring out where a person falls on the trans spectrum (transvestite/transgender/transsexual etc ), this is a very complex and confusing process that involves a lot of personal introspection. For people who have dabbled with cross-dressing, the desire to wear the opposite gender's clothes can either fade, stay the same, or lead to more questioning about their own gender identity. It appears that the latter is what has happened to you, Clay.
After being so comfortable with cross-dressing since the fifth grade, your curiosity about becoming more feminine has grown over time and now has you second-guessing many things: Am I more than just a cross dresser? Am I actually a woman inside but never really considered it until now? What kinds of steps can I take to start transitioning towards this new gender identity and do I even want to risk it? These are all questions that you've probably been asking yourself in the last little while. If not, take the time to try and figure out whether or not you're happy simply as a transvestite/cross-dresser or if you need to further explore the idea that you might be a woman inside. Another issue you brought up that needs to be considered is getting support from your family. If they were supportive of you, would you feel more at ease in taking steps to transition? Other than familial support, what other barriers are there that are preventing you to explore further?
Since you are still questioning your feelings at this stage, it would be best if you started to get yourself in touch with other people that have transitioned. You mentioned having an MTF friend who has transitioned. If you are good friends and trust her, ask her about her transition. Find out more about her process. See if she has other friends that have gone through their own process. You'll notice in the trans community, everyone has a different story and rarely are any two transitions alike. Finding out more about how they went about it and especially where they were able to find support is crucial to helping you decide what you would like to do yourself.
Once you take the time to better inform yourself about transitioning and setting
yourself up your own support system, that's when you can start thinking about
telling your family. When you become better connected with the trans community in your area, find out how people dealt with coming out to their family. See if you can strategize the best way you can give them the news. Read up on coming out as trans, or even coming out as gay since these processes have similar phases to consider.
Take the time to really think things over. Many people who struggle with the idea of
being trans seek professional counseling to help them work through their feelings and situation. This is a great way to work through your feelings in a confidential and safe setting. Whatever you choose to do, it's important that you figure out (whether on your own, or with the help of friends or professionals) what needs you have to have fulfilled so that you can get to resolving your feelings of depression and isolation.
Hopefully this response will help you get the ball rolling on working towards what will make you happiest. If you would like, you can always write us back to tell us what city or state you live in so that we can offer support resources available in your area (this will of course remain confidential). Otherwise, you are welcome to write again if you want to give us any additional details or updates. Good luck on your journey!
Kay Wo for AlterHéros