While I am not certain about having an effeminate voice, when I was a child I had a lisp. It was horribly embarassing when I had to pronounce the TH sound. It took a little bit of speech therapy but by the time I hit my 20s it was more or less gone.... although to this day, I avoid saying the word “sixth”.
Barbara Walters had an incurable speech impediment. She couldn't say "r"s. It's impossible to cure so she avoided the words with an "r." Learn to avoid the "th" sound. The Germans don't have that sound in their vocabulary at all. Instead of saying THINK or THING, they say "tink" and "ting." It's just part of sounding German.
People who know you and/or love you don't care really about your lisp. It's really what you say and how you say things that count, isn't it?
***I avoid saying the word sixth.****
QUICK! Say ...”The sixth sheik’s sixth sheep’s sick!”
I had to type that slow as even I can’t say it.