You are not alone. I noted many complaints on injuries in this forum in this season.

My second team also suffered the worst injury problem ever. I have full roster 22 players. But at one point, I still only had 5 substitutes (i.e. 7 players injured) after all my treatment packs were consumed. I have no solution but tolerate. My rest packs were also consumed quickly. I had to continue to use poor form players. My team dropped to middle of the league table early in the season. But the problem will go if you have patience. The injury rate eventually decreased. My team raised back to 2nd in league table (actually I only have 2 draws early in the season). I can also save some stocks of rest and treatment pack again.

In my experience, injuries spread like virus. A series of injuries often occur at the same time. In such case, I will use my treatment packs for long term injuries only as it is more efficient. For injuries within 3 days, I usually let them recover naturally. Some players are really more injury prone than the others. You have to consider whether to keep them even though they may be high in quality.