Labels such as heterosexual and homosexual are based on the concept of a gender binary, in that they also implicate the gender of the person identifying with them, and don't really apply to the situation you have described (attraction to multiple genders). If you don't fit into it then terms like 'straight' and 'gay' can sometimes feel disingenuous. Often people who don't identify as male or female are more comfortable defining their sexuality with terms such as NBLM and NBLW (non-binary people loving men/women, respectively). There are also terms in existence that don't include the source of attraction in them so don't implicate your own gender - they just refer to the person you're attracted to, e.g. androsexual can mean attraction to men and/or masculine-presenting people and gynesexual can mean attraction to women and/or feminine-presenting people. Although if you're attracted to multiple genders then the more well-known bi/pansexual sound like they would fit just fine.
Personally, I'm somewhere outside of the gender-binary and consider myself homosexual although my relationships often pass as straight based on how I present on any given day. I use this term because I'm exclusively attracted to my assigned gender at birth, don't identify as the opposite, and only date people who self-identify as bi/pan/homosexual.