Question on rhythm when improvising

Saxophone student here, I've been playing for about three years. I struggle with rhythm when improvising. If I start playing a solo, I quickly lose track of whether I'm on the downbeat or somewhere else in the measure. The same happens with knowing where I am in the form of the standard. It’s hard for me to focus on what I’m playing and the global rhythm and structure of the song.

What exercises would you recommend to improve this?

Thank you very much!