Hi Miho!
ユーコネクトの英語コーチのアーサーです！
まずは、「ごめんなさい」の部分です。
「ごめんなさい」は「ごめん」より丁寧な言い方なので、
「I'm sorry」または「I apologize」と言います。「I apologize」の方は丁寧です。
もし「ごめん」または「ごめんね」というと、
Sorryだけでいいです。
〜てごめん（なさい）
〜して＋ごめん（なさい）というとき、英語でSorry for 〜またはSorry that 〜になります。
I'm sorry for being late.
I'm sorry that I was late.
I'm sorry for making a mistake.
I'm sorry that I made a mistake.
ポイント：
「for + 名詞（またはing動詞）」
「that + 文章」
forの方が言いやすいと思うのでおすすめします。
心配かける
心配する＝worry.
相手に心配している状況にさせたのでmake (someone) worriedと言います。
I'm sorry that I made you worried.
I'm sorry for making you worried.
I'm sorry for making you worry.
I'm sorry that I made you worry.
よろしくお願いします！
応援しています！
アーサー
I feel bad that I made you so worried. I'm really sorry!
It's my fault I caused you all this worry. I'm so sorry!
Any of these statements is adequate and, depending on the circumstances, may be followed by something like:
I'll try to keep you better informed.
I'll try to be more considerate in future.
状況次第では上記の表現はすべて正確に相手に伝わるでしょうが、以下のように繋げると良いでしょう。
I'll try to keep you better informed. これからはちゃんとお伝えしておきます。
I'll try to be more considerate in future. 次からはもっと考えて行動します。
Both of the sentences are a wonderful way to apologize for worrying your host family. Sometimes things come up in our schedule or we are not able to communicate with the person waiting for us. After apologizing, we can explain what caused us to be late and express that we will try and not make them worry again.
"I feel horrible for making you worry, I am sorry"- When we feel bad about something, we can say that "I feel horrible." "Horrible" is just a synonym for "bad" and it can be replaced with words such as: terrible, atrocious.
"I apologize for making you worry about me. "- We use the word "apologize" as a substitute for the word "sorry". It sounds better and it is a more formal statement. This word can be used in the previous sentence as well. You would the change it to "I feel horrible for making you worry, I apologize."
I hope you didn't get too worried about me, I was perfectly safe
It is normal for our friends or families to be worried about us if we are living abroad, and we have not made contact in a while. If you are staying with a host family then the family you are staying with would feel very responsible for you because you are new to the surroundings of the city you are staying in. If you are late arriving home then it is normal that the family would get a bit worried
We can use these two sentences to let the family know that you were perfectly safe.
Here is an example of this sentence being used in context: I forgot to say that I was going out last night. Sorry for worrying all of you! Next time I will make sure to let at least one of know that I will be heading out.
アメリカ合衆国 
日本 
イギリス 
南アフリカ 
アイルランド 
ニュージーランド 
