I've been thinking about you, since I haven't heard from you lately.
I worried about you, since you haven't sent me any messages.
I haven't heard from you lately, so I missed you.
「最近連絡がないからあなたのことが気になってた」は、
①I've been thinking about you, since I haven't heard from you lately.
②I worried about you, since you haven't sent me any messages.
③I haven't heard from you lately, so I missed you.
などが伝わりやすいと思います。
①②は友だちにも使えます。③が一番恋人向けですね^^
I was wondering how you were because I hadn't heard from you in ages
I worried because I hadn't heard from you in forever
I was wondering how you were because I hadn't heard from you in ages=長い事連絡がないからどうしてるのか気になってた
hear from〜=〜から連絡がある
wonder=気になる、〜について考える
in ages=長い事、久しく
「懐かしい!」と言ったニュアンスが少しあります。例:
I haven't played this game in ages=このゲーム長らくやってなかったな
I worried because I hadn't heard from you in forever=ずっと連絡ないから心配したよ
forever=永遠に、一生
少し大げさに聞こえるかもしれませんがその方が寂しさが伝わります。