ばかりだ

ばかりだ says that a change keeps going in one direction and shows no sign of stopping: "just keeps getting…". It follows the dictionary form of a verb of change – ふえる増える, へる減る, あがる上がる, or an adjective with なる – and the trend is almost always an unwelcome one.

The verb before ばかり is the dictionary form whatever the tense; the past goes on だ.

• × 悪くなったばかりだ → 悪くなるばかりだ

With the た-form it is a different pattern, たばかり: "has only just got worse".

ばかりで, mid-sentence

Before a second clause, ばかりだ becomes ばかりで. The second clause usually spells out the bad side: it isn't going back.

ばかりだ, たばかりだ and てばかりいる

All three use ばかり and the attachment form tells them apart. The dictionary form gives a trend. The た-form gives something that has only just happened. The て-form with いる gives someone doing nothing but one thing.