「昔はよく～した」はused to~と言います。
used toには、「（今はそうではないけど）」
「昔はよく～した」とうニュアンスを含んでいます。
「プロ野球の試合を観に行く」は
watch a professional baseball gameです。
野球やサッカーを観戦する時はwatchを
使います。
参考になれば幸いです。
*I often watched the baseball league.- Often means frequently.
*I'm a fan of professional baseball. -A fan is a person who supports sports, person.
A: Jack you like baseball so much.
B: Oh yes I breathe, eat and sleep baseball.
例文
*I often watched the baseball league.
野球の試合をよく見に行っていました。
Oftenは頻繁にということです。
例文
*I'm a fan of professional baseball.
私はプロ野球ファンです
A fanはスポーツや人を応援する人のことです。
例文
A: Jack you like baseball so much.
ジャック、あなたは本当に野球が好きだね
B: Oh yes I breathe, eat and sleep baseball.
ああ、そうだよ、野球に夢中だよ
I used to watch professional baseball games all the time.
I always used to watch professional baseball games.
「発生率」か「度数」に関する話では、英語のネイティブ・スピーカーは誇張されている表現や単語をよく使います。
例えば、「よく（often)」の代わりに「いつも（always か all the time）を使い、
そして「あまり〜しない（rarely, hardly ever)」という意味を伝いたい時は「全然（never)」と言います。
例）I never go shopping
は
「あまりショッピングに行かない」
という文です。
"I used to watch professional baseball games all the time."
"I always used to watch professional baseball games"
はただ、「昔はよくプロ野球の試合を観に行きました」ということです。
「発生率」か「度数」に関する話では、英語のネイティブ・スピーカーは誇張されている表現や単語をよく使います。
例えば、「よく（often)」の代わりに「いつも（always か all the time）を使い、
そして「あまり〜しない（rarely, hardly ever)」という意味を伝いたい時は「全然（never)」と言います。
例）I never go shopping
は
「あまりショッピングに行かない」
という文です。
"I used to watch professional baseball games all the time."
"I always used to watch professional baseball games"
はただ、「昔はよくプロ野球の試合を観に行きました」ということです。
These example sentences above make clear that you are attending baseball games **in person** -- not just watching them on TV. If you were always at home on the couch, you might say
-- I used to watch the game on television every night
-- I loved to sit on the couch at home and watch the game.
上記の例文はあなたが野球の試合をテレビで見るのではなく、「自分で」 **in person** 見ていることを伝えています。家のソファーで観戦するタイプだったならば、次のように言えるでしょう。
-- I used to watch the game on television every night.
（昔は毎晩テレビで試合を観戦しました。）
-- I loved to sit on the couch at home and watch the game.
（家のソファに座って、試合を見るのが大好きでした。）
I used to go to watch the baseball league all the time
I used to go to the pro baseball games all the time
The 'ballpark' is the official name given to the stadium ground baseball is played on. As the majority of stadiums are for professional use only, its obvious that you are talking about watching professional games.
'Pro' is the abbreviated way to say 'professional'. You could say that a professional baseball player was a 'pro baller' which is slang for 'really good at something', and it can be used outside of a baseball context too.
To say 'all the time' does not literally mean you spent all of your time watching the games, but it suggests you went frequently.
I frequently went to watch professional baseball in the past
Explanation: You may use the phrase, 'in the past...' when talking about an earlier occurrence. 'Frequently' is an adverb with similar meaning to 'regularly.'
Example sentence:
"In the past I frequently went to church, but not these days."
解説：過去の事柄について話す時は、「昔は」を表す 'in the past...'という表現が使えるでしょう。頻繁に 'Frequently'は定期的に 'regularly.'と似た意味を持つ副詞です。
例文：
"In the past I frequently went to church, but not these days."
（昔は頻繁に教会に行きましたが、最近はあまり行きません。）
"I used to watch professional baseball games often"
"I use to often watched the baseball league as I enjoy them"
"I use to love to watch professional baseball games"
If you use to go to watch professional baseball games often and you wanted to explain this to whomever you are speaking to you could state one of the following: "I used to watch professional baseball games often", "I use to often watched the baseball league as I enjoy them" or "I use to love to watch professional baseball games".
昔よくプロ野球の試合を見に行っていたなら、次のように説明できます。
"I used to watch professional baseball games often"（昔はよくプロ野球の試合を見ました）
"I use to often watched the baseball league as I enjoy them"（昔はプロ野球が好きでよく試合を見ました）
"I use to love to watch professional baseball games"（昔はプロ野球の試合を見るのが好きでした）
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