The idiom can/could help Verb-ing is a Negative Polarity Item, which means it can only occur with a negative, but the negation is not part of the idiom.
The construction itself requires the verb phrase can help (or could help in the past), followed by a Gerund (-ing) clause as its object complement. Only those verbs can occur -- no other modals but can or could, and no other verb but help.
- He couldn't/I can't help noticing the crane.
- *He/I may not help noticing the crane.
- *He/I won't help noticing the crane.
- *He couldn't/I can't assist noticing the crane.
That's the idiomatic construction. It can optionally take a reflexive object
- He couldn't/I can't help himself/myself.
But normally this only occurs when the action that is being discussed is already part of the context, taken for granted, as in the answer to a question:
- Q: Why did you give him the finger? ~ A: (Because) I couldn't help myself.
So the reflexive usually takes the place of the object gerund complement. If you want to include the complement, then you don't want the reflexive, normally. It's only there to add emphasis, and the idiom still means 'control oneself', whether the reflexive pronoun's there or not. And if it is there, it gets in the way; as you noticed.
So, instead of keeping the unnecessary reflexive and then horking the gerund clause in under some preposition -- which only adds syllables and complicates the parsing -- I'd just drop it all and say, simply,
- I couldn't help playing soccer.
instead of either (1) or (2) above.