How can i fix my belly button so it looks more open like a button rather than a slit or frown?

A tummy tuck can improve the shape of your belly button. So can an umbilicoplasty, which would be less invasive. Liposuction might help but it would be difficult to say without a physical exam. 

Hello and thank you for your question. There are many different options to improve belly button aesthetics.   The most important aspect is to find
a surgeon you are comfortable with.  I recommend that you seek consultation with a
qualified board-certified plastic surgeon who can evaluate you in person.
Best wishes and good luck.
Richard G. Reish, M.D.
Harvard-trained plastic surgeon

Hello. You may be a candidate for an umbilicoplasty which is a procedure to change the shape of your belly button. Not sure if you also have an umbilical hernia. You'll need to be examined by a BCPS. DrBurnett#realself100

Both a Tummy Tuck and Umbilicoplasty can help reshape the size of your belly button. However if you do decide to have children, pregnancy can change things dramatically.  So if considering a baby in the next few years best to wait.