You might be mispronouncing the alveolo-palatal consonants (Pinyin j, q, x) as denti-alveolars (Pinyin z, c, s), which is common among foreigners whose native languages lack alveolo-palatals, since it's hard to figure out how to correctly curl your tongue without an explicit description.

The reason that would make your speech appear feminine is that some young Beijing women pronounce those consonants similarly, probably in a (potentially unconscious) attempt to sound cute. The closest analog in English I can think of is swapping word-initial l for w ("wuv", "widdle").

The phenomenon in Chinese is known as 女国音; I became aware of it through the talk page of the Wikipedia article on Standard Chinese phonology: https://en.wikipedia.org/wiki/Talk:Standard_Chinese_phonolog...