You are how old? Do you have diabetes, high cholesterol, thyroid disease, take medications for bp? You should get a checkup with your PCP as erections can be a good barometer for a man's health.
Anxiety is never good for erections or arousal. Your head is in the wrong place. You need to be relaxed. You can learn to relax without drugs with relaxation therapy with biofeedback. Vigorous exercise can also help show you what it feels like to be relaxed.
I am 35. Fit and do exercise
If you are fit and doing exercises, learn the folloeing exercises and do it regularly.
Male Deer Exercise
Do yoga postures for sexual strength(Google for the website)
Stop sexual activity at least for one month. Do not take products like viagra.You can ruin your life with addiction of there drugs.