In my native language, we have a saying - a stone will get a wretched person, going uphill

It never rains but [what] it pours.

it never rains but it pours [phrase]

You can use the expression it never rains but it pours to mean that several unfortunate events often happen at the same time.

[COBUILD Advanced English Dictionary] ...............

it never rains but it pours [in British]

events, esp unfortunate ones, come together or occur in rapid succession

[Collins English Dictionary; op cit]

Obviously, the implication is that the unfortunate events happen over the same region / to the same people.

Misfortunes never come singly TFD

Prov. Bad things tend to happen in groups.

As in:

I already told you that my wife lost her job. Well, misfortunes never come singly; our house was robbed last night.

Not a popular one but it is worth considering:

Bend over, here it comes again. BOHICA is its Acronym.

Referring to something bad which is about to happen again or as usual.

The Free Dictionary defines as:

Trouble isn’t over yet, there is more on the way. TFD

• It snowed ten inches yesterday. BOHICA. They forecast another foot!

Out of the frying pan and into the fire

From a bad situation to one that is much worse
American Heritage Dictionary

Alternatively, there's kick a man when he’s down. Macmillan defines it as:

to treat someone badly when they are already in a weak position

This is more particular to heaping more misfortune on an already struggling individual.