Top, no you haven't left it too late
The way to get bf going now is to keep your baby skin to skin with you, and be gentle, responsive and patient with her. Your midwife should encourage and support you.
This is only day 5 - you have plenty of time before your milk just goes, and it is early days for your baby to get her breastfeeding act together. There's no mad rush!
Getting milk is not a question of 'sucking hard enough' but of being latched on and positioned in a way that the baby's own instinctive sucking action removes the milk effectively.
Babies love breastfeeding and do it best when they are not messed about with - so keep her in a position where she can show you her feeding cues and you can just help her pop on.
Breastfeeding is absolutely not a cause of clinginess - babies differ in their clingy behaviour because they differ in personaility and needs.
You may need to continue to give formula if you are not confident she is getting milk, but this would be something to talk about with the midwife. It may be you can cut it right down, and then out. The more formula you give, the less chance there is of builing up and maintaining a supply that meets your baby's needs.
Expessing and giving by bottle is another way of getting the good stuff into your baby - but breastfeeding is so much more than that, and I really hope you'll find this out