Your stats aren't really an issue I don't think. Your strength only needs to be the minimum requirement to wield whatever sword you want to use. With your current stats you could wield a heavier sword.

If I had to guess I'd say you're probably struggling with the play style of a pyro, so perhaps some tips:

1) Pyro spells aren't particularly quick to cast so making sure you have distance to cast them. I would suggest using melee against enemies that could easily close the gap.

2) However, distance isn't always your friend. Boss fights tend to be a bit more difficult at a distance. Bosses are generally more aggressive the further away you are. Id suggest in boss fights you stay close to them, rolling their attacks and casting at the end of a flurry if you have enough stamina.

3) Imo armour sucks in ds. If you can have a weight % of less than 30% your rolls will have more i-frames. Sure, you might get more hurt when you do get hit, but rolling is OP. As you level more you get more defense anyway.

4) try to start engagements with your strongest attack. Usually you have more time as the enemy is moving towards you. Use this time to deal max damage with spells.

5) Finally, don't feel like you have to only use Pyro. With your stats you can also cast miracles, so why not make use of them too? Perhaps a weapon buff spell, or healing spell could help give you an advantage!