No and Yes. Casting spells from scrolls doesn't use a slot, it just uses up the spell and there aren't any limits on how many scrolls you can use.

Does using a spell scroll count as casting a spell?

As stated in this FAQ, when using magic items, such as scrolls, wands, or magic rings and necklaces (and pretty much all magic items), you do not count as having cast the spell yourself, you merely activated the magic item, which in turn, cast the spell, using the caster level set in the item.

Do all spells use spell slots?

Every class uses Spell Slots to cast their Spells. ... Some classes don't need to prepare their spells, meaning they can cast any spell they know, whenever they want, as long as they have the Spell Slots for it. Warlocks are the oddball — they don't have Spell Slots of different levels.