If you worry by the time you get degree you will be old, then
don't go for ITE > Poly > Degree.
Can try A Level > Local U, but you really have to work hard
if you want to go local U. If cannot go local U, still can take
Private Degree.
Or Private Diploma > Private Degree, but this path is really
expensive, for sure you need to work and study part-time, unless
your parents got money to support. By the way, I took this path,
spent about 30K+ (course fees, bank interest, transport and etc),
not much money and tiring because working and studying. I was worse
than you, only PSLE when I finished NS... Or like some of my
campmates, they finished their private diploma / degree during NS,
don't know how they do it but they did.
Now I have a degree at 27 years old, could have gotten it at 25
or 26, but I didn't have enough money to pay for it at that time,
so I saved up for about 1 or 2 years.
But no matter which path you take, if your parents are not going
to support you or you prefer to work and pay by yourself, then
start saving money now. It sucks when you want to study but don't
have money.
And since you are going NS, you will have a lot of time to think
and find out, who knows things might be different after 2 years of
NS.