New Runners

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Hi I have been on my weight loss journey for several years and have just recently started running again. I have had asthma my entire life and am overcoming the exercise asthma issues. Here is my issue...after I do about 2 miles I just don't feel like I can go further. My legs get tired and I feel like I can't go any further. Looking for support and suggestions as to how I can progress to 3 miles and 4 and so on...